Learn Hardcore Spanish (Latin America): Mi esposa y mi suegra se llevan muy bien porque hablan con sinceridad. - My wife and my mother-in-law get along very well because they speak sincerely.

llevar alone usually means to carry / to wear / to take.
- Ellos llevan cajas. → They are carrying boxes.
llevarse bien changes the meaning to to have a good relationship.
- Ellos se llevan bien. → They get along well.

So you need the reflexive pronoun se to express this idea of relationship, not physical carrying.

What exactly does llevarse bien express? Is it the same as to like each other?

Llevarse bien focuses on how the relationship works in practice, not just emotional liking.

se llevan muy bien → they get along very well (they cooperate, there is harmony, few conflicts).
It usually implies that they like each other, but it emphasizes:
- good communication
- few arguments
- day‑to‑day compatibility

So it is close to they really get along, more than just they like each other.

Why is it se llevan and not se lleva?

The verb agrees with the subject:

Subject: Mi esposa y mi suegra → two people → third person plural.
Third person plural of llevarse in the present: se llevan.

If it were only one person:

Mi esposa se lleva bien con mi suegra. → My wife gets along well with my mother‑in‑law.

There the subject is mi esposa (singular), so you use se lleva.

Why is hablan (present simple) used instead of están hablando (present progressive)?

In Spanish, the present simple (hablan) is commonly used for:

habits
general truths
repeated behavior

Here hablan con sinceridad means they (generally) speak honestly, describing their usual way of communicating, not what they are doing right now.

Están hablando con sinceridad would focus on what is happening right this moment, which is not the idea in this sentence.

What is the difference between porque and por qué, and why is porque used here?

porque (one word, no accent) = because (introduces a reason).
- …se llevan muy bien porque hablan con sinceridad.
por qué (two words, with accent on qué) = why (used in questions).
- ¿Por qué se llevan tan bien? → Why do they get along so well?

In the sentence, we are giving a reason (because they speak honestly), not asking a question, so porque is correct.

Why is it con sinceridad and not an adverb like sinceramente? Are both correct?

Both are grammatically correct and natural:

hablan con sinceridad → they speak with sincerity.
hablan sinceramente → they speak sincerely.

Nuance:

con sinceridad sounds slightly more like a quality or value they apply when speaking.
sinceramente is a straightforward adverb, a bit more compact.

In everyday speech, both are fine and mean practically the same here.

Do you really need to repeat mi in mi esposa y mi suegra? Could you say mi esposa y suegra?

In modern Spanish, repeating the possessive is the clearest and most natural:

mi esposa y mi suegra → my wife and my mother‑in‑law (two different people).

If you say mi esposa y suegra, it sounds incomplete or odd in most contexts, and could even be confusing (it might sound like one person who is both your wife and your mother‑in‑law).

So the safest and most natural pattern is:

mi X y mi Y when you are talking about two different people or things.

Why is it muy bien and not mucho bien?

Because muy and mucho are used with different kinds of words:

muy modifies adjectives and adverbs:
- muy bien (very well)
- muy feliz (very happy)
mucho modifies:
- nouns: mucho trabajo (a lot of work)
- verbs: trabaja mucho (he works a lot)

So with bien (an adverb), you must use muy, not mucho.
mucho bien is only possible in special expressions like hacer mucho bien (to do a lot of good), but not after llevarse.

Could the sentence use sinceramente instead: …porque hablan sinceramente?

Yes, that is perfectly correct:

Mi esposa y mi suegra se llevan muy bien porque hablan con sinceridad.
Mi esposa y mi suegra se llevan muy bien porque hablan sinceramente.

Both mean essentially the same. Any difference is very subtle:

con sinceridad slightly highlights sincerity as a value present in their conversations.
sinceramente feels a bit more neutral and adverb‑like.

Native speakers use both.

What does suegra mean exactly, and are there related forms I should know?

Suegra means mother‑in‑law.

Related words:

suegro → father‑in‑law
suegros → parents‑in‑law (as a couple or group)
nuera → daughter‑in‑law
yerno → son‑in‑law

So mi esposa y mi suegra is my wife and my mother‑in‑law.

Why is esposa used instead of mujer? Are mi esposa and mi mujer the same?

Both can mean my wife, but there are regional and stylistic differences:

mi esposa:
- common and neutral in Latin America
- also understood in Spain
- a bit more formal or standard
mi mujer:
- very common and natural in Spain in everyday speech
- also used in some parts of Latin America, but less uniformly and can sound more colloquial or regional.

Since you specified Latin American Spanish, mi esposa is a very safe and standard choice.

Could you add ellas and say …porque ellas hablan con sinceridad? Would that change the meaning?

You can say:

Mi esposa y mi suegra se llevan muy bien porque ellas hablan con sinceridad.

This is grammatically correct. The meaning is almost the same, but:

Without ellas, Spanish assumes the subject from the verb ending (hablan).
Adding ellas gives light emphasis to they, as in:
- They speak honestly (implying maybe other people do not).

In neutral style, Spanish often omits subject pronouns when the subject is clear, so the original version is more typical.