Walaupun sibuk, dia tetap menepati janji kepada ibunya.

Yes. Walaupun means although / even though / even if, depending on context.

In this sentence, walaupun sibuk means although (he/she is) busy.

A very close synonym is meskipun. In most everyday sentences, walaupun and meskipun can be used interchangeably:

• Walaupun sibuk, dia tetap menepati janji kepada ibunya.
• Meskipun sibuk, dia tetap menepati janji kepada ibunya.

Both sound natural.

Indonesian often omits words that are understood from context.

So walaupun sibuk is a natural shortened form of:

• walaupun dia sibuk = although he/she is busy

Because the main clause already has dia, Indonesian does not need to repeat it. Both are correct:

• Walaupun sibuk, dia tetap menepati janji kepada ibunya.
• Walaupun dia sibuk, dia tetap menepati janji kepada ibunya.

The shorter version is very common and sounds smoother.

Tetap means still, nevertheless, or all the same.

It emphasizes that the person kept the promise despite being busy. Without tetap, the sentence would still make sense, but tetap adds the idea of persistence or consistency.

Compare:

• Walaupun sibuk, dia menepati janji kepada ibunya.
  = Although busy, he/she kept the promise to his/her mother.

• Walaupun sibuk, dia tetap menepati janji kepada ibunya.
  = Although busy, he/she still/nevertheless kept the promise to his/her mother.

So tetap strengthens the contrast.

Menepati janji is a very common expression meaning to keep a promise or to fulfill a promise.

It is the natural Indonesian collocation. Learners should remember it as a set phrase:

• menepati janji = to keep a promise
• ingkar janji = to break a promise

So even if you understand the individual words, it is best to learn menepati janji as one common unit.

Menepati is built from:

• tepat = exact, correct, on time
• plus the suffix -i
• plus the prefix meN-

This gives menepati.

A useful point for learners: when meN- is added to a word beginning with t, the t usually disappears:

• tepati → menepati

This is a normal sound/spelling change in Indonesian verb formation.

In meaning, menepati often means to fulfill, to keep, or to adhere to, especially with things like promises, agreements, or schedules.

Because janji kepada seseorang is a common way to say a promise to someone.

Here:

• janji = promise
• kepada ibunya = to his/her mother

So menepati janji kepada ibunya literally means to keep the promise to his/her mother.

You may also hear pada in some contexts, but kepada is very standard when referring to a person as the recipient or target of something.

Yes. In this sentence, ibunya most naturally means his mother or her mother.

Important point: Indonesian dia and -nya do not show gender. So:

• dia = he / she
• ibunya = his mother / her mother

You only know the gender from context, not from the word itself.

Also, -nya can sometimes mean the in other contexts, but here the possessive meaning (his/her) is the natural one.

Both dia and ia can mean he or she, but they are used a little differently.

• dia is very common in everyday speech and writing.
• ia is more formal or literary.

Also, ia is mainly used as a subject, while dia is more flexible.

So in this sentence, dia is the most natural everyday choice.

The comma is standard and helpful here because Walaupun sibuk is an introductory subordinate clause.

So the structure is:

• Walaupun sibuk, = Although busy,
• dia tetap menepati janji kepada ibunya. = he/she still kept the promise to his/her mother.

In informal writing, people sometimes omit commas, but in careful writing the comma is a good choice.

Yes. Indonesian allows the subordinate clause to come first or last.

These are both natural:

• Walaupun sibuk, dia tetap menepati janji kepada ibunya.
• Dia tetap menepati janji kepada ibunya walaupun sibuk.

The meaning stays basically the same.

Putting walaupun sibuk first gives stronger emphasis to the contrast right away.

Yes. Sibuk is broader than just one English word.

Depending on context, it can mean:

• busy
• occupied
• tied up
• having a lot to do

In this sentence, busy is the most natural translation, but the Indonesian word itself is flexible.

It is basically neutral standard Indonesian.

Nothing in it is slangy, and nothing is especially stiff or ceremonial either. It would work well in:

• conversation
• school materials
• news-style writing
• general formal writing

That makes it a very useful model sentence for learners.

Usually, yes.

Both can be understood, but menepati janji is the more common and idiomatic expression for keeping a promise.

• menepati janji = very natural, standard
• memenuhi janji = possible, but less typical in many contexts

So if you want the safest everyday phrase, use menepati janji.