Brat i sestra ne moraju uvijek biti u pravu, ali moraju slušati jedno drugo.

Because brat i sestra means brother and sister, so together they make a plural subject: they.

• brat = brother
• sestra = sister
• brat i sestra = brother and sister

So Croatian uses the 3rd person plural verb:

• moraju = they have to / they must

This is just like English:

• The brother is...
• The sister is...
  but
• The brother and sister are...

Here ne moraju means don’t have to / do not need to.

So:

• moraju = they have to / they must
• ne moraju = they do not have to

That is an important point, because English learners often expect a stronger meaning like must not, but Croatian usually expresses that idea differently, often with ne smiju:

• Ne moraju biti u pravu. = They do not have to be right.
• Ne smiju... = They must not / they are not allowed to...

So in this sentence, the idea is not prohibition. It is lack of necessity.

Because after morati (to have to / must), Croatian normally uses an infinitive.

So the pattern is:

• morati + infinitive

Examples:

• Moraju biti u pravu. = They have to be right.
• Moraju slušati jedno drugo. = They have to listen to each other.

This is similar to English have to + verb:

• have to be
• have to listen

The finite verb is moraju, and the following action stays in the infinitive.

Biti u pravu is a fixed expression meaning to be right.

Literally, it is close to to be in the right.

• biti = to be
• u = in
• pravu = right / the right

So Croatian often uses this whole phrase where English uses just be right.

Examples:

• Ti si u pravu. = You are right.
• Ona nije u pravu. = She is not right.
• Ne moraju uvijek biti u pravu. = They do not always have to be right.

This is a very common expression, so it is best learned as a chunk: biti u pravu.

In u pravu, pravu is in the locative case after u.

That is because this expression originally works like in the right.

So even though learners usually remember the whole phrase as one unit, grammatically it reflects:

• u + locative

You do not usually need to analyze it every time, though. For practical learning, it is better simply to memorize:

• biti u pravu = to be right

as a fixed idiom.

Yes, Croatian word order is fairly flexible, and adverbs like uvijek (always) can often move around.

In this sentence:

• Brat i sestra ne moraju uvijek biti u pravu...

the placement sounds natural and means do not always have to be right.

You may also hear slightly different placements depending on emphasis, but this version is neutral and natural.

A useful thing to notice is that uvijek here modifies the whole idea of being right in all situations, not just the verb in some narrow mechanical way.

So the meaning is:

• They are not required to be right all the time.

In Croatian, ne is usually written separately before the verb:

• ne moraju = do not have to
• ne slušaju = do not listen
• ne znaju = they do not know

So this is normal.

English speakers sometimes look for a one-word negative form, but Croatian usually uses ne + verb as two words.

There are a few special forms elsewhere in the language, but for a sentence like this, ne moraju is exactly what you should expect.

Jedno drugo means each other or one another.

So:

• slušati jedno drugo = to listen to each other

This is a reciprocal expression, showing that the action goes both ways:

• the brother listens to the sister
• the sister listens to the brother

English uses one phrase, each other, and Croatian has several forms depending on grammar and context. In this sentence, jedno drugo is the natural form for this pair.

Because reciprocal expressions in Croatian change form depending on gender, number, and case.

With a mixed pair like brat i sestra, Croatian often uses jedno drugo for each other.

This can feel strange to English speakers, because English does not change each other at all. But Croatian does.

So in this sentence, it is best to learn the whole phrase:

• slušati jedno drugo = listen to each other

You may meet other forms of this reciprocal expression in other sentences, but here jedno drugo is the form to focus on.

Because slušati means to listen, while čuti means to hear.

That distinction is similar to English:

• slušati = to listen (active, intentional)
• čuti = to hear (perceive sound)

In this sentence, the meaning is about paying attention to one another, so slušati is the correct verb.

Compare:

• Moraju slušati jedno drugo. = They have to listen to each other.
• Čuju jedno drugo. = They hear each other.

Those are not the same idea.

Because Croatian has no articles like a/an/the.

So:

• brat can mean brother, a brother, or the brother
• sestra can mean sister, a sister, or the sister

The exact meaning depends on context.

In this sentence, English naturally uses Brother and sister or The brother and sister, but Croatian simply says brat i sestra.

This is normal throughout the language.

Yes, depending on context.

Since Croatian has no articles, brat i sestra could refer to:

• a brother and sister
• the brother and sister
• brother and sister in a general sense

The exact English translation depends on the situation. If the meaning has already been given to the learner, then the Croatian itself does not force one article choice.

So the grammar point is:

• Croatian leaves article information unstated
• English usually has to choose one

Ali means but.

It connects two contrasting ideas:

• ne moraju uvijek biti u pravu = they do not always have to be right
• ali moraju slušati jedno drugo = but they have to listen to each other

So the sentence contrasts:

• being right is not always necessary
• listening to each other is necessary

That contrast is exactly what ali marks.

Not in a normal complete sentence like this.

The second clause needs its own finite verb, so:

• ali moraju slušati jedno drugo

is the correct full structure.

Croatian can sometimes omit repeated words in certain contexts, but here keeping moraju makes the grammar clear and natural.

It also emphasizes the contrast nicely:

• They do not always have to be right,
• but they do have to listen to each other.