Sweetie, I have very few limits in my sex life, but for you, this is SUCH a bad idea, for all the reasons listed above.
The fact that you asked us here, in this forum about it, tells me inside YOU think this is a bad idea.

SO DON'T DO IT.

Also, genetically, while there is only a slight increase in risk of a child born with birth defects when two cousins get busy, the risk is there.

Nurse Wanda

__________________
"I wondered, am I a lesbian, am I straight, or bisexual? Then I realized that I am just a slut.
So where's MY parade?"

---Margaret Cho