Is there a way to come out without it just being for no reason?

Really weird to describe but I feel like I want to tell my sister and possibly my mom that I'm gay but I don't know why. I can't think of an actual reason to tell them but I just want to. But I also feel like I don't NEED to come out. Idk its just confusing but is there a way I could bring it up? I have no idea what to say and even though I can't foresee them reacting negatively but I'm still so damn nervous....