That's no reason to champion the wardens though. Die young, become impotent, endlessly fight darkspawn... just so you can feel "speshul"?
If that's what magic has to done to his mentality, I really do pity him.
edit: lol, I meant infertile. Thankfully, impotency is off the list.
I don't really champion the Grey Wardens. In fact, I rather dislike that the protagonist of DA:O had to be one at all. In that character's place, I'd simply take my chances going batsh*t crazy on the surface and leave the order entirely, because f*ck the Deep Roads and Grey Warden traditions. I'd like to think that this is something my character would have done, especially since I chose nothing but dialogue that protests. Though I ironically import this character into Awakening, it does seem to honor the outcome you chose for DA:O proper, since if you choose to leave at the coronation, the Warden-Commander will step down and depart, presumably for good.
But anyway, from Hawke's perspective, the gruesome details of being a Grey Warden may be a total mystery, and that's really the only thing I will consider. Aside from that, I consider their personalities and their roles. Carver is a soldier out of Ostagar who was going to fight darkspawn anyway, so he comes along. Bethany, however, is not, and while Kirkwall is swarming with Templars, they are a touch safer than a deep dwarven hellhole filled with monsters, and so I would abide by Leandra's wishes. Then there's Carver's bellyaching about wanting purpose and being overshadowed by Hawke, which I have little to no stomach for. The way I see it, if he wants to brood and feel like he needs to prove something to himself, then he can come along and put his sword to use, and maybe there will be too many darkspawn for him to have time to p*ss and moan. But once he contracts the taint, I would not permit him to die if it could be helped.
As for infertility, I suppose that would be his problem, should he actually be concerned about it. I wouldn't care about a lack of prospects for nieces and nephews anyway.