It's called incest and it's illegal.
sex
There is no major religion that allows marriage between siblings. In most cultures and religions, such relationships are considered incestuous and forbidden due to concerns about genetic abnormalities in offspring and societal taboos.
Your sister's husband is your brother-in-law. Your brother-in-law's brother is not related to you and neither are his children. But he is your sister's brother-in-law and his children are your sister's nieces and nephews.
Your sister's daughter and your sister's brother are niece and uncle to each other. The daughter is the niece of the brother and the brother is uncle to the daughter.
Your sister-in-law is either the wife of your brother or the sister of your spouse. If you have more than one brother, and your sister-in-law is the wife of one brother, then she is the sister-in-law of the other. If your sister-in-law is the sister of your spouse, she has no direct relationship to your brother. He can call her "my brother's sister-in-law", or "my nephew's aunt."
A brother and a sister, both being children of the same parents, are siblings.
yes their brother and sister, but they still make out and have sex
No. As there is no insurable interest between brother & sister it is not possible to take a policy on an adult brother by his sister.
No, there is no relationship between the two of you.
the blind beggar was a girl. they were brother and sister. the brother had no brother ..... just a blind girl beggar as a sister.
A niece is the daughter of your brother or sister. A cousin is the son or daughter of your parent's sister or brother.
Your brother's son is your nephew, but the English language has no term for a relationship between you and the wife of your nephew. If you have to refer to her other than by name, the best you can do is call her "my nephew's wife" or "my brother's daughter-in-law."