These are grave grave problems. :rofl:
Well, it's once again religion vs. biology. Honestly, I can't think of any reasons why one shouldn't have sex with one's cousin except the rules society implanted in us. Biologically and psychologically there is nothing wrong with wanting to fuck an attractive relative. Only problem is, that the offspring is more likely to catch a genetic disease because the gene pool is the same.
This kinda reminds me of the Louis C. K. skit where he talks about fucking a monkey...