Well, just know you're not as bad as some people.
I remember once this girl in college who at a Christian youth group was telling people that she was adopted from China and that the reason her parents put her up for adoption is because she's the product of incest.
Her mother and father were full siblings.
She went on to talk about how she's had bone surgery because she developed bumps on her bones from a genetic disorder as result from the incest.
I don't know why some people share so much, but a kiss is nothing compared to something so personal family history/dirty laundry.