My partners family member told me that my partner wasn't actually biologically related to a close family member. My partner does not know about this. I was shocked to be told this and was told not to mention to him. I feel terrible knowing this and he doesn't. It really upsets me to think no one has told him. Should I tell him? I worry it will upset him and cause people to fall out with me, but I also feel terrible he doesn't know. I don't want him to find out one day and know I have also kept it from him. I really don't know what to do