Is it normal to have sex with your sibling of the opposite sex?

i married a woman on her third marriage , her brother lived with her as a baby sitter. turns out he was tapping that shit pretty regular basis. he told me he wanted some gay sex with me. i caught them at it one time in the living room. he was up her butt . he was also doing his niece's ass almost every day as well she was just ten or eleven . he was a gay top. no car totally dependant on his sister. her little butt hole had a pernamanent gape. i was so embarrassed to take her to a pediatrician because she had pin worms, she saw that anal gape and i new she saw molestation but she did nothing to report it. not a damn thing, she probably thought it was my dick in that hole . well my point is incest is mainstream world wide. As is adult child sex . its all covered up by people in power , Like doctors. well i moved out and divorced her ugly ass a year latter. not because of the incest but because i didnt want to be around when that ten year old got pregnant and get the blame. in their world blood is thicker than water.