Брати іноді сваряться один з одним, але швидко миряться.

Context tells you.

• брати́ = brothers
• бра́ти = to take

In normal writing, Ukrainian usually does not mark stress, so both appear as брати. But here the rest of the sentence makes it clear that this is a plural noun: сваряться and миряться are plural verbs, so they need a plural subject. That subject is Брати = brothers.

It is the nominative plural of брат.

• singular: брат = brother
• plural: брати = brothers

It is in the nominative because it is the subject of the sentence: the brothers are the ones doing the actions.

Іноді means sometimes.

Yes, its position is fairly flexible. For example:

• Брати іноді сваряться...
• Іноді брати сваряться...

Both are natural. Putting іноді in a different place may slightly change emphasis, but the basic meaning stays the same.

Сваряться is the 3rd person plural present tense form of сваритися.

So it means:

• they quarrel
• they are quarreling
• in this sentence, more naturally: they sometimes quarrel

Because the subject брати is plural, the verb is also plural.

The ending -ся is a reflexive marker, but in many verbs it does not literally mean themselves. Very often it helps create a verb with a reflexive, passive, or reciprocal meaning.

Here, сваритися means to quarrel. In this sentence the meaning is reciprocal: the brothers quarrel with each other.

A useful comparison:

• сварити = often to scold
• сваритися = to quarrel

So -ся is part of the normal dictionary form of this verb.

It means each other or one another.

Literally, it is something like one with another. Ukrainian often uses this kind of expression to show reciprocity.

So:

• Брати сваряться один з одним = The brothers quarrel with each other

This phrase is very common when you want to make the mutual action explicit.

Because the preposition з here means with, and with requires the instrumental case in Ukrainian.

So:

• з одним = with one another

That is why you see одним, the instrumental form, after з.

Yes. з, із, and зі are variants of the same preposition, all meaning with or from, depending on context.

The choice usually depends on pronunciation and what sounds easiest before the next word.

Here з одним sounds natural, so з is used. In other contexts you may see:

• із
• зі

The meaning does not change.

Миряться is the 3rd person plural present tense of миритися.

It means:

• they make up
• they reconcile
• they become friends again

So швидко миряться means they make up quickly.

Because the sentence describes a repeated/habitual situation, not a single completed event.

• сваряться = imperfective
• миряться = imperfective

With іноді = sometimes, imperfective is the natural choice: it describes what usually happens.

If you were talking about one completed episode, Ukrainian would often use perfective forms, for example:

• посварилися = they had a quarrel
• помирилися = they made up

So this sentence is about a pattern: they sometimes quarrel, but they quickly make up.

Because але means but, and in Ukrainian a comma is normally placed before it when it joins two clauses or two parts of a compound sentence.

So:

• Брати іноді сваряться один з одним, але швидко миряться.

This is standard punctuation.

Yes, Ukrainian word order is fairly flexible.

For example, you could also say:

• Іноді брати сваряться один з одним, але швидко миряться.

That still means the same thing. The version you were given is a very natural neutral order.

Word order changes usually affect emphasis, not the core meaning.

Because Ukrainian has no articles like English the or a/an.

So брати can mean:

• brothers
• the brothers

Which one sounds best in English depends on context. Ukrainian leaves that to the situation rather than using an article.