Assuming that you are your wife are not related, except by marriage (you and your wife are not cousins, etc.), that would mean your sister and your wife's nephew are in no way blood relatives. The Bible does not put limitations on a man and a woman who are not related getting married.
Yes.
No. Because he is your cousin and its wrong to date family
Yes. You are the aunt of your sister's children and anyone you marry is their uncle.
The bible is very strict on this point. It only allows a man to have a wife. But if she dies then he can marry again.
Islam is one of those religions that believe it is acceptable to marry your cousin. It should be noted, however, that "cousin brother" and "cousin sister" have no meaning in the English language. Your brother or sister is a person who has the same parents you do. Your cousin is someone who is the child of your parents' brother or sister, or of your grandparent's brother or sister.
Well to be honest its up to you whether you want to marry someone related to you
No, it is illegal to marry your sister anywhere in the world.
yes you can marry because she is your cosin sister
Yes, if his wife is dead or divorced he could marry her sister.
Yes. You can marry your LIVE wife's sister if you want to, provided that you are both free to marry.
Yeah, but it would be a little weird
Christianity, jewish Most every religion allows you to marry.