That's a tough one! In my circle of friends and aquaintances there are a lot of people who used to go out with someone else, and then after they split eventually ended up with someone else in their group of friends.
I guess it all depends on how often you & your cousin hang out, and on what grounds they split up - if it's amicable then I don't see why he should hve a problem with it (once he got over her, otherwise it would hurt to see her with you), but if they end up hating each others' guts then it would be weird for him and uncomfortable for both (that's given you hang out/go out with your cousin a lot, like a big circle of friends type thing)
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25, female, AS with attentional dysfunction
Inhibited Perfectionist
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thanx for the advice. 
