with plurals, de becomes des.....

Question

Why isn't it "Nous ne faisons pas partie DES amis" as "ses amis" is plural? But then I guess that would apply to "de les amis", so what's going on here?

Accepted Answer

Bonjour Steven,
Possessive adjectives don't contract, so you'd say nous faisons partie de ses amis, je fais partie de mes invités, etc.
Or if you're not using the adjective, then yes, you say des amis, des invités.

Answer

Hi Steven, in negative expressions, we always use de or d' irrespective of plurality. See this lesson: du, de la, de l', & des all become de or d' in negative sentences

Answer

Merci, une réponse très rapide!
But how do we deal with posessive articles when it's not negative?
So, "nous faisons partie (de ses) amis = .....des amis; je fais partie (de mes) invités = ....des invités?