"He lives with his parents."
Translation:Abita con i suoi genitori.
They are used interchangeably in terms of residence:
- Mia sorella vive/abita in questa casa
- Noi viviamo/abitiamo in città
- Loro vivono/abitano insieme
But if residence is irrelevant then stick to vivere
- Gli squali vivono nell'acqua (Sharks live in water)
- Sto vivendo un momento difficile (I am living/going through a difficult moment)
- Loro vivono felici (They live happily)
with one parent i.e. mio padre, mia madre, you don't use the article, but with parents, grandparents etc in the plural, you use it like this: i miei genitori, i miei nonni, so your sentence would correctly become 'lui vive con i suoi genitori'. sometimes it's best to accept a rule rather than understanding it right away, you learn faster that way. when you've seen it enough times you have a lightbulb moment and understand it.
You need it for plural family members, but not single ones—except: + You need it for 'loro' family member. + You need it for a modified family member, e.g. la mia mamma, la mia sorellini. + You need it if an extra adjective is included before the family member, e.g. la mia bella madre.
It could be someone else's parents: vive coi genitori della sua ragazza -> vive coi suoi genitori.
But you have a point.
In general, Italian doesn't use the possessive extensively as English does: 'he brushes his teeth' -> si lava i denti; 'I touch my head' -> mi tocco la testa...
Both vive coi genitori and vive coi suoi gentiori are OK. However, I think the most common expression would be vive con i/coi suoi, leaving genitori out of the sentence altogether.