"Do you want to bring them their lemon?"
Translation:Voulez-vous leur apporter leur citron ?
The sentence is a bit of une chienne. Leur can be a possessive pronoun, as used before "citron." Leur can also be an indirect object pronoun. ("les" is a direct object pronoun).
-Qui va apporter ce citron à mes amis? Voulez-vous leur apporter leurs citrons?"
The indirect object pronouns are me, te, lui, nous, vous, leur.
The first corresponds to 'them' and the second to 'their'. it's combarable to the English sentence "Bring her her lemon" where 'her' is used twice, but with different meanings.