Welcome to our forum.
Coming out can be a tough job; not all polyamorists do it. Take me for example, I'm still in the closet. I'd kind of like to come out, but that's not what my companions want, so I am willing to honor their wishes. I talk to them sometimes when the subject comes up.
I guess there will be different opinions about the cousin thing. Me personally, I don't have a problem with it. As long as the situation is consensual all around between the three of you. But, as you've already seen, you may be in for some heat about the cousin thing, as well as the poly thing, when you come out to your family.
I'm sure you are not a slut or a whore; certainly not from reading your post. I suspect that a lot more people are "inwardly poly" than realize it.
Anyway, continue reading various threads and stuff here, and don't hesitate to post any thoughts or questions you may have. I'm glad you could join us.
Love means never having to say, "Put down that meat cleaver!"