my husband's brother have a relationship with his niece, gross?

Some families are into stuff like that. You married into one.

Watch out for grandpa!

Her kids are going to call him Uncle Daddy.

Are they blood related or just via marriage?

If blood related, I believe it to be illegal in most of the US. They can still marry (if a State which does not require blood testing) because there last names are different and therefore, no one would relate them as relatives. Personally, I find it distorted and perverted. I feel it goes against the laws of the universe.

If they are niece is only a niece through marriage then no problem!

If I were you, I would try to stay open minded and be as civil as possible about it unless they ask for your opinion. If it is that offensive and you are not close to these people, you could ask your husband to have them not come over. But you never know why or what goes on between two people and it may not be anyone's business.

DO NOT let an INCESSTIAL man or women into your house. It is WRONG & BARBARIC. Urge your husband to talk to his brother about this. It is your husbands duty to protect his niece from his FILTHY brother.

if they are blood related it is incestuous , but it isn't your fault ,don't be ashamed. If you do not want them in your home tell your husband his incestuous family members are not welcome in your home.

if they are just related through marriage then it is fine and not your business.

he's banging his Niece ??? are they related ?? if they're not related and she's 18 then it's not that big of a deal.

It is illegal .