Ο ξάδερφός μου άφησε μουστάκι, αλλά η γιαγιά μου λέει ότι ήταν πιο ωραίος πριν.

In Greek, it is very common to use the definite article with family members and other specific people:

• ο ξάδερφός μου = my cousin
• η γιαγιά μου = my grandmother

Greek usually says the cousin of mine, even where English just says my cousin. So the article is not extra here; it is the normal Greek pattern.

Also, ο shows that ξάδερφος is masculine singular nominative.

The basic noun is ξάδερφος. When you add the weak possessive pronoun μου, Greek often writes an extra accent if needed to keep the stress pattern clear:

• ο ξάδερφος
• ο ξάδερφός μου

This is a normal spelling rule with possessive clitics like μου, σου, του etc.

Because Greek possessive pronouns of this type normally come after the noun:

• ο φίλος μου = my friend
• η μητέρα μου = my mother
• το σπίτι μου = my house

So Greek does not usually say the equivalent of my cousin with the possessive first. The standard order is:

article + noun + possessive pronoun

The verb αφήνω basically means leave, let, or allow. But in expressions about hair, beard, mustache, etc., it can mean let it grow:

• άφησε μουστάκι = he grew a mustache
• άφησε γένια = he grew a beard
• άφησε τα μαλλιά του μακριά = he let his hair grow long

So the idea is not literally left a mustache, but rather let a mustache grow.

Άφησε is the aorist form of αφήνω. Here it gives a simple past event:

• άφησε μουστάκι = he grew a mustache

The Greek aorist is often used for a completed event in the past, similar to the English simple past. It does not focus on duration; it just presents the action as a whole.

Greek often leaves out the article with professions, roles, and also with some objects in set expressions like this one.

So:

• άφησε μουστάκι = grew a mustache

is natural Greek.

You could sometimes hear άφησε ένα μουστάκι in a different context, but that would sound more like emphasizing a mustache as a specific new feature. In this sentence, the bare noun is the most natural wording.

Μουστάκι is neuter:

• το μουστάκι

In this sentence, it appears without the article, but its gender is still neuter in general. Knowing the gender matters because adjectives and articles would match it in other contexts, for example:

• ωραίο μουστάκι = nice mustache
• το μουστάκι του = his mustache

Because the sentence combines:

1. a present-time reporting verb
   
   • η γιαγιά μου λέει = my grandmother says
2. a description of how he was earlier
   
   • ότι ήταν πιο ωραίος πριν = that he was better-looking before

So the grandmother is speaking or holding that opinion now, but what she is talking about concerns the past.

This is completely normal in both Greek and English:

• She says that he was more handsome before.

Yes. Both ότι and πως can introduce a that-clause after verbs like λέω:

• λέει ότι...
• λέει πως...

In this sentence, ότι is perfectly standard. In everyday Greek, πως is also very common. The meaning here is the same.

Just remember that πως can also mean how, depending on context, while ότι only means that.

In Modern Greek, the most common way to make a comparative is:

• πιο + adjective

So:

• ωραίος = handsome / nice / good-looking
• πιο ωραίος = more handsome / better-looking

Greek does have some more learned or formal comparative forms for certain adjectives, but πιο + adjective is the normal everyday pattern and the one learners should get comfortable with first.

Because the adjective describes the cousin, who is masculine:

• ο ξάδερφος → masculine
• therefore ωραίος → masculine singular

The adjective agrees with the person being described, not with μουστάκι.

Compare:

• ο ξάδερφος είναι ωραίος
• η ξαδέρφη είναι ωραία
• το παιδί είναι ωραίο

Here πριν means before in the sense of earlier / previously:

• ήταν πιο ωραίος πριν = he was more handsome before

It works here as an adverb referring to an earlier time. Greek does not need an extra word like before now; πριν by itself is enough in this context.

Do not confuse this with πριν used before a clause, such as:

• πριν φύγω = before I leave / before leaving

Not always. Ωραίος is a very flexible adjective. Depending on context, it can mean:

• nice
• good-looking
• handsome
• pretty
• great
• lovely

In this sentence, since the grandmother is commenting on the cousin’s appearance, πιο ωραίος naturally means something like:

• more handsome
• better-looking

So the exact English word depends on context, not just the dictionary meaning.

Αλλά is the normal word for but:

• ..., αλλά ... = ..., but ...

It works very much like English but to contrast two ideas:

• he grew a mustache
• but his grandmother thinks he looked better before

So there is no special hidden grammar here; it is a straightforward contrast word.

Yes, it sounds natural and idiomatic.

Especially natural features are:

• ο ξάδερφός μου / η γιαγιά μου with article + noun + μου
• άφησε μουστάκι for grew a mustache
• λέει ότι for reporting someone’s opinion
• πιο ωραίος for the comparative
• πριν meaning before

So this is a good example of normal spoken and written Modern Greek.