Honestly? This is on the same level of gay marriage.
Marriage is in place to have a strong family unit that you can utilize to raise kids.
Gay people shouldn't be allowed to adopt kids, and they shouldn't be allowed to get married. I don't see anything wrong with being gay if thats your choice, but you shouldn't be able to expose kids to that lifestyle (it is unnatural no matter what anyone says) or get the benefits of a married couple.