Learn Hardcore Spanish (Latin America): A veces mi hermano y yo nos peleamos por cosas pequeñas. - Sometimes my brother and I fight over small things.

Pelear on its own can mean to fight in a more general sense:
- El ejército pelea. – The army fights.
Pelearse is used for people fighting with each other, like siblings, friends, etc.:
- Mi hermano y yo nos peleamos. – My brother and I fight (each other).

The nos shows that the action happens between the members of the subject: mi hermano y yo. So nos peleamos is best understood as we fight each other.

What exactly does the nos in nos peleamos do?

Nos is the first-person plural reflexive pronoun: ourselves / each other.

In mi hermano y yo nos peleamos:

mi hermano y yo = subject (my brother and I → we)
nos = reflexive pronoun for we
peleamos = we fight

Together, nos peleamos means we fight each other or we get into fights.
Without nos, peleamos would just be we fight, without clearly expressing the idea that it’s mutual or between the two of us.

Can nos peleamos also mean we fought (past tense)? How do I know if it’s present or past?

Yes, nos peleamos can be both:

Present tense: we fight / we argue
Preterite (simple past): we fought / we argued

You know from context and from time expressions:

A veces mi hermano y yo nos peleamos.
With a veces (sometimes), it clearly describes a habitual action → present:
Sometimes my brother and I fight.
Ayer mi hermano y yo nos peleamos.
With ayer (yesterday), it clearly refers to one past event → past:
Yesterday my brother and I fought.

So nos peleamos is ambiguous on its own, but adverbs like a veces, ayer, siempre, etc., clarify the meaning.

Why is it por cosas pequeñas instead of sobre cosas pequeñas or de cosas pequeñas?

In this context, por is the natural preposition to express the reason, cause, or motive for the fight.

pelearse por algo = to fight over something / because of something

So:

Nos peleamos por cosas pequeñas.
= We fight over small things.

Using other prepositions changes the meaning:

pelear sobre algo – more like to argue about a topic (a discussion or debate)
- Pelean sobre política. – They argue about politics.
pelear de algo – not used in this sense; sounds wrong for fight over something.

For reasons or causes, Spanish commonly uses por:

Discutimos por dinero. – We argue about money.
Se enojó por un comentario. – He got mad because of a comment.

Why is it cosas pequeñas and not pequeñas cosas? Does the word order change the meaning?

By default, adjectives in Spanish follow the noun:

cosas pequeñas = small things (descriptive, neutral)

Some adjectives can go before or after the noun, with a nuance:

pequeñas cosas is possible, but it sounds more stylistic or emotional.
It can suggest little things in a more subjective, “not important” or even affectionate sense, depending on context.

In everyday neutral speech, describing size or importance, noun + adjective is the standard:

casas grandes – big houses
problemas serios – serious problems
cosas pequeñas – small things

So cosas pequeñas is the most standard, neutral way to say small things.

Why isn’t there an article? Why not por las cosas pequeñas?

Spanish often uses a bare plural noun (no article) when speaking in general:

por cosas pequeñas = over small things (in general, not specific ones)

If you say por las cosas pequeñas, it sounds like:

because of the small things (some particular, known small things),
or a more specific set that both speakers know about.

Compare:

Nos peleamos por cosas pequeñas.
We fight over small things (in general).
Nos peleamos por las cosas pequeñas que haces.
We fight over the small things that you do. (Now it’s specific.)

Why is it mi hermano y yo instead of yo y mi hermano?

Both orders are grammatically correct, but mi hermano y yo is far more natural.

In Spanish (and in polite English), it’s typical to mention the other person before yourself when listing people:

Mi hermano y yo – my brother and I
Mis amigos y yo – my friends and I
Mi mamá y yo – my mom and I

Yo y mi hermano is not wrong, but it sounds less natural and sometimes childlike or self-focused. Native speakers overwhelmingly prefer X y yo.

Why is there no nosotros? Shouldn’t it be A veces nosotros nos peleamos?

The subject nosotros is already clear from the verb form peleamos and from mi hermano y yo.

In Spanish, subject pronouns (yo, tú, él, nosotros, etc.) are usually omitted because the verb endings already show who the subject is:

(Nosotros) nos peleamos.
(Nosotros) comemos.
(Nosotros) vivimos aquí.

You can say A veces nosotros nos peleamos, but:

It sounds like extra emphasis on nosotros (we, as opposed to others).
In this simple sentence, native speakers just don’t need it.

Mi hermano y yo completely identifies the subject, so nosotros would be redundant.

Why is a veces at the beginning? Could I say Mi hermano y yo nos peleamos a veces?

Yes, both are correct:

A veces mi hermano y yo nos peleamos.
Mi hermano y yo nos peleamos a veces.

A veces is an adverbial expression (sometimes). In Spanish, these can often move around in the sentence without changing the basic meaning. The difference is in rhythm and slight emphasis:

A veces mi hermano y yo nos peleamos.
Slight emphasis on sometimes at the start.
Mi hermano y yo nos peleamos a veces.
Feels like a more neutral statement; the sometimes comes as a comment at the end.

Both are very natural.

How is nos peleamos formed grammatically?

It’s pelearse (reflexive verb) in the present indicative, first person plural:

Infinitive: pelearse
Remove -se, conjugate pelear → peleamos (we fight)
Add the appropriate reflexive pronoun for nosotros → nos
Result: nos peleamos = we fight (each other)

Full present conjugation of pelearse:

yo me peleo
tú te peleas
él/ella/usted se pelea
nosotros/nosotras nos peleamos
vosotros/vosotras os peleáis (mainly Spain)
ellos/ellas/ustedes se pelean

Why is it mi hermano and not mis hermano?

Possessive adjectives in Spanish agree with the thing possessed, not with the possessor.

mi is singular
mis is plural

Since hermano is singular:

mi hermano – my brother
mis hermanos – my brothers

The fact that I (the possessor) am one person doesn’t affect this. What matters is the noun:

mi casa / mis casas
mi amigo / mis amigos

Could I say Mi hermano y yo peleamos por cosas pequeñas without nos? Would it sound wrong?

You could say it, and it’s still understandable, but it’s less natural and slightly changes the feel.

Nos peleamos focuses on fighting each other, mutual conflict.
Peleamos alone is more like we fight in general, and doesn’t automatically express with each other.

In practice, when talking about people who fight with each other (siblings, partners, friends), Spanish strongly prefers the reflexive:

Mi hermano y yo nos peleamos por cosas pequeñas. ✅ (natural)
Mi hermano y yo peleamos por cosas pequeñas. 😐 (understandable but less idiomatic here)

So the version with nos is what natives normally use in this context.

Where does the reflexive pronoun go in negative or longer sentences with nos peleamos?

With a simple conjugated verb (no infinitive/gerund), the reflexive pronoun goes before the verb, even in negatives:

No nos peleamos por cosas pequeñas.
We don’t fight over small things.
A veces nos peleamos por cosas pequeñas.
Casi nunca nos peleamos.

If you add an infinitive or gerund, you have a choice:

Vamos a pelearnos. / Nos vamos a pelear. – We’re going to fight.
Estamos peleándonos. / Nos estamos peleando. – We are fighting.

But in the original sentence, with only one conjugated verb, the correct order is always nos peleamos, never peleamos nos.