Put it up for adoption if you're man enough to have sex with someone, but not enough of a man to take responsibility, for the second time I might add. Or just kill it like you did it's sibling. People honestly make me sick these days, and I hope that in some turn of events your wife can't have children after this and when you want them, you can't have them. I'm sure there's millions of families out there that can't have children out of infertility that would gladly trade places with you in this situation.
Oh, and what's the point of marrying someone if you don't eventually want to settle down and have kids with said person.