El meu nebot m'ha fet un petó i després ha començat a riure.

In Catalan, a possessive usually comes with the definite article:

• el meu nebot = my nephew
• la meva germana = my sister
• els seus amics = his/her/their friends

So unlike English, Catalan normally says the my nephew literally, even though in real meaning it is just my nephew.

m'ha is a contraction of em ha:

• em = to me / me
• ha = has

Before a vowel or silent h, em becomes m'.

So m'ha fet un petó literally works like has given me a kiss.

Here em is the person receiving the kiss.

Fer un petó is a very common Catalan expression meaning to give someone a kiss or simply to kiss.

Literally:

• fer = to do / to make
• un petó = a kiss

Catalan also has the verb besar, which means to kiss, but fer un petó is extremely natural and very common in everyday language.

They are both in the present perfect:

• ha fet = has done / has given
• ha començat = has started

This tense is formed with:

• haver as an auxiliary
• plus a past participle

So:

• ha
  • fet
• ha
  • començat

In Catalan, this tense is often used for completed past actions, especially when they feel connected to the present or are relatively recent.

Yes. The verb fer is irregular, and its past participle is fet.

Examples:

• he fet
• has fet
• ha fet

By contrast, començar is regular here:

• començar → començat

So in the sentence, one participle is irregular (fet) and one is regular (començat).

Because començar normally takes a + infinitive when it means to begin/start doing something.

So:

• començar a riure = to start laughing
• començar a parlar = to start speaking
• començar a córrer = to start running

English does not need a preposition here, but Catalan usually does.

After començar a, Catalan uses the infinitive, not the gerund.

So the correct pattern is:

• començar a riure

not

• començar a rient

Even though English says started laughing, Catalan literally says started to laugh.

Because the subject is already clear. In this sentence, el meu nebot is understood to be the subject of both actions:

• m'ha fet un petó
• ha començat a riure

Catalan often leaves out repeated subjects when they are obvious from context. Repeating it would usually be unnecessary unless you want extra emphasis.

Després means afterwards, then, or later.

It shows the order of events:

1. the nephew gave a kiss
2. then he started laughing

So it helps connect the two actions in sequence.

Yes. A very natural alternative would be:

El meu nebot em va fer un petó i després va començar a riure.

That uses the periphrastic past, which is extremely common in Catalan for completed past actions.

Very roughly:

• ha fet / ha començat = present perfect
• va fer / va començar = simple completed past, expressed with va + infinitive

Which one sounds more natural can depend on dialect, style, and how connected the action feels to the present.