I dont think cheating the way to go... why not just talk to your husband on how you feel????(╯°Д °)╯╧╧
Idk bout you guys but if I found out my brother was adopted and his dad told him that he had to marry me or my 2 other sisters I know for damn sure the last thing I would be thinking is "oh yes since we are blood related let's fuck" like it doesnt matter if you're not blood related that's still your sibling that you grew up with. (╯°Д °)╯╧╧ also wtf is wrong with the parents!? They literally raised him like their son and then suddenly they are just okay with everything, that just means they never actually saw him as their child to begin with.
As she should
i meant to upvote sorry