Oh hell no. Considering that I seem to react very badly to people being too similar to me and that I enjoy my relationship with my fiancée because she is different (while accepting of the ways in which I am different). Similar enough to get along, different enough to be interesting.
Anyway, what would you talk about? How can you exchange ideas when neither of you have anything to say the other doesn't already know? How dull would you both be in bed if neither of you ever came up with anything surprising? It wouldn't even be worth playing video games, neither of you is better than the other, and you always pick the same character/race/class/armour/avatar/whatever.
Plus, you know, it IS incest in the literal "Spread the genes wide" sense, there's a fair chance of anything recessive but horrible hiding in my DNA coming out to play in any potential children of that unholy union.