So this weekend me and my siblings went up to my (blood) cousins wedding in Chicago. It was a fun party drinking dancing etc. My sister had started talking and flirting with this boy there named Jimmy. Jimmy is my aunts husbands son from

another marriage. My sister went up to his room with him and slept with him after basically pursuing him all night. Me and my other siblings were like wtf? This is our uncles son, we are really close to our uncle he’s been around our whole life’s. She sees no problem in her actions but me and my siblings think its a little gross even tho they aren’t cousins by blood only cousins by marriage. What do you think?