Learn Hardcore Indonesian: Sepupu saya yang lain menikah di gereja setelah dua tahun tunangan, karena keyakinan keluarganya berbeda. - Another cousin of mine gets married in a church after two years of being engaged, because her family’s belief is different.

Saying sepupu saya lain is not natural here. You normally need yang before lain when you mean the other one in this kind of noun phrase.

Compare:

Dia pilih baju yang lain. = She chose the other dress.
Ada orang lain di rumah. = There is another person in the house.
(Here lain comes after orang, but there is no yang because it’s not specifying a particular “one from an already known group,” just “some other person.”)

So for “my other cousin,” use sepupu saya yang lain, not sepupu saya lain.

What is the difference between sepupu saya yang lain and sepupu saya lainnya?

Both are grammatical, but they have different nuances.

sepupu saya yang lain
= my other cousin / another cousin of mine
→ Sounds like you are picking out one (or some) other cousin in contrast to one already mentioned.
sepupu saya lainnya
= literally the others of my cousins / the rest of my cousins
→ More collective: “the other cousins (of mine)” as a group, contrasting with a first group already mentioned.

Examples:

Satu sepupu saya tinggal di Jakarta. Sepupu saya yang lain tinggal di Surabaya.
One cousin lives in Jakarta. My other cousin lives in Surabaya.
(Talking about individuals.)
Beberapa sepupu saya sudah menikah. Sepupu saya lainnya masih sekolah.
Some of my cousins are already married. The rest of my cousins are still in school.
(Talking about groups: some vs the rest.)

Why is di used in menikah di gereja? Could you say menikah gereja without di?

You need di here because gereja is a place, and di marks location: at / in.

menikah di gereja = get married in a church / at church

Without di, menikah gereja is ungrammatical. Verbs that involve actions in a place almost always take di + place:

bekerja di kantor = work at the office
belanja di pasar = shop at the market
makan di restoran = eat in a restaurant

You could make it more specific:

menikah di gereja Katolik = married in a Catholic church
menikah di sebuah gereja kecil = married in a small church

But di must stay.

Does menikah mean the same thing as kawin? Which is more polite?

Both can mean to marry / get married, but their usage is different:

menikah
- More neutral / polite / standard.
- Common in writing, formal speech, and polite conversation.
- Used in the given sentence: menikah di gereja.
kawin
- More casual/colloquial, and can sound less polite or less refined.
- Also used in animal contexts (animals mating), so sometimes it can sound crude in the wrong context.
- Among close friends it’s often fine: Kapan kamu kawin? = “When are you getting married?” (colloquial).

In careful or formal Indonesian, especially in writing or with people you don’t know well, menikah is safer and more appropriate.

In setelah dua tahun tunangan, what is tunangan exactly? Is it a noun or a verb? Why is there no verb like bertunangan?

Tunangan can function both as:

A noun:
- tunangan = fiancé(e)
- bertunangan = to be engaged
A kind of stative verb/adjective-like verb meaning to be engaged in everyday speech.

In setelah dua tahun tunangan, it’s understood as (being) engaged:

setelah dua tahun tunangan
≈ after (they had spent) two years engaged

Indonesian often drops ber- when the meaning is clear and the shorter form is common in speech:

Mereka sudah lama tunangan.
= They have been engaged for a long time.

A more explicit (and slightly more formal) version would be:

setelah bertunangan selama dua tahun
setelah dua tahun bertunangan

All of these are acceptable. The original is just a bit more casual/natural-sounding.

Is the word order menikah di gereja setelah dua tahun tunangan fixed, or can I move setelah dua tahun tunangan to the beginning?

The word order is flexible. Both are correct:

Original:
- Sepupu saya yang lain menikah di gereja setelah dua tahun tunangan, ...
  Focus is first on how/where they married (at church), then when (i.e. after how long).
Alternative:
- Setelah dua tahun tunangan, sepupu saya yang lain menikah di gereja, ...
  Focus is first on the time condition (“After being engaged for two years…”), then what happened.

In Indonesian, time or condition expressions like setelah…, ketika…, kalau… can often be placed:

at the beginning: Setelah dua tahun tunangan, ...
or after the main clause: ..., setelah dua tahun tunangan.

Both sound natural; it’s more about emphasis and style.

Why is there a comma before karena in ..., karena keyakinan keluarganya berbeda? Is the comma required?

The comma separates the main clause from the reason clause:

Sepupu saya yang lain menikah di gereja setelah dua tahun tunangan,
= main clause
karena keyakinan keluarganya berbeda.
= reason clause (because…)

In writing, it is standard (and clearer) to use the comma there. It makes it easier to see that what follows is an explanation/reason.

You could also put the karena-clause at the beginning, usually also with a comma:

Karena keyakinan keluarganya berbeda, sepupu saya yang lain menikah di gereja setelah dua tahun tunangan.

Leaving out the comma in the middle is possible in very informal writing, but it’s less clear and not recommended for learners. So for now, treat the comma as required.

What does keyakinan mean? How is it different from agama?

Both relate to religion, but they’re not the same:

agama
= religion (as a system / official category)
Examples: agama Islam, agama Kristen, agama Hindu
keyakinan
= belief(s), conviction, faith
It can mean:
- religious beliefs, or
- more generally, personal convictions, what someone strongly believes.

In the sentence karena keyakinan keluarganya berbeda, the idea is:

“because his/her family’s beliefs/faith are different”

This can imply religious background, denomination, or more general spiritual or ideological beliefs, without naming a specific agama. It’s slightly more abstract and sometimes more polite/indirect than saying agama keluarganya berbeda (their religion is different).

In keyakinan keluarganya berbeda, why is there no adalah or itu? How does this sentence work grammatically?

Indonesian often drops adalah and uses a simple noun/adjective as the predicate.

Breakdown:

keyakinan keluarganya = his/her family’s beliefs (subject)
berbeda = different (predicate; an adjective functioning as a verb: “are different”)

So structurally it’s:

[Subject] [Adjective]
→ Keyakinan keluarganya berbeda.
→ (Their) family’s beliefs are different.

You could say:

Keyakinan keluarganya itu berbeda.
Keyakinan keluarganya adalah (sesuatu yang) berbeda.

But these either sound a bit heavier, or slightly off; the natural way is exactly what you see: keyakinan keluarganya berbeda (no adalah needed).

Why is it keluarganya and not keluarga dia? Are they the same?

They are very close in meaning, but keluarganya is more natural here.

keluarganya
- keluarga = family
- -nya = his/her/their (also “the”)
  → usually interpreted as his/her family from context
keluarga dia
- literally “family he/she”
- also understandable as his/her family, but sounds a bit more casual/childish in many contexts.

In standard Indonesian, the -nya possessive is extremely common and often preferred:

rumahnya = his/her/their house
ibunya = his/her mother
keluarganya = his/her family

You might still hear keluarga dia in speech, but here keluarganya is smoother and more idiomatic.

How do we know who keluarganya refers to? The cousin or the partner?

On its own, keluarganya is ambiguous: it could mean his/her family (either the cousin’s family or the fiancé(e)’s family).

Indonesian often relies on context, not grammar, to make this clear. In a longer text or conversation, earlier sentences would usually make it obvious whose family is meant.

If you must be explicit, you can specify:

karena keyakinan keluarga sepupu saya berbeda
= because my cousin’s family’s beliefs are different

karena keyakinan keluarga tunangannya berbeda
= because his/her fiancé(e)’s family’s beliefs are different

But in natural Indonesian, people only add that extra wording if there’s real risk of confusion; otherwise keluarganya is enough.

Does karena keyakinan keluarganya berbeda explain why the wedding was in a church, or why they waited two years to get married?

The Indonesian sentence is actually ambiguous in a similar way to English.

menikah di gereja setelah dua tahun tunangan, karena keyakinan keluarganya berbeda.

This could be understood as:

They got married in a church (rather than in some other way) because the family’s beliefs are different.
They waited two years before marrying because the family’s beliefs are different.
Or both factors (church wedding + 2‑year engagement) are consequences of those beliefs.

Usually, listeners infer the most plausible meaning from wider context (e.g. a story about interfaith marriage, family pressure, etc.). Grammatically, the karena clause simply gives the reason for the whole preceding situation, not tied to just one small piece of it.

How is past time expressed here? There is no past tense marker, but the meaning is clearly in the past.

Indonesian generally does not change the verb form for tense. Instead, time is understood from:

time expressions: dua tahun, kemarin, tahun lalu, etc.
context (storytelling is often in past time by default)

In the sentence:

menikah di gereja setelah dua tahun tunangan
→ the sequence setelah
- dua tahun already shows a past sequence of events, so learners interpret it as got married after being engaged for two years.

If you want to make past-ness more explicit, you can add adverbs:

Sepupu saya yang lain sudah menikah di gereja setelah dua tahun tunangan.
= My other cousin has already married in a church after two years of engagement.

But sudah isn’t required; the original is already natural and clearly refers to past events in most contexts.

What is the overall level of formality of this sentence? Would it sound natural in everyday conversation?

The sentence is in a neutral, slightly formal style:

Words like menikah, keyakinan, berbeda are neutral to slightly formal.
The structure is clear and standard, not slangy.

You could absolutely say this in everyday conversation, especially in a thoughtful or serious context (talking about family, religion, etc.). To make it more casual, people might:

shorten things, add sih, kan, etc.
use tuh, gitu, or more colloquial phrasing.

For example, more casual speech could be:

Sepupu gue yang satu lagi nikah di gereja, udah dua tahun tunangan soalnya keyakinan keluarganya beda.

But as given, the sentence is perfectly natural in both spoken and written Indonesian with a neutral tone.