The more I think about the guy, the more I don't think he can be excused in any way, shape or form. We don't know the whole story, but couldn't he have begged her to keep them? Couldn't he have promised her the moon if she would give birth to his children? When she refused, couldn't he have said, "I can't stop you, but I won't participate in the murder of my own children?" I just don't see where he gets off as being a sympathetic character. A real man would have acted so much differently. I think it's even WORSE that he went along with it--supported her is the PC phrase--because he was at least subliminally aware that the triplets were living beings. But who wins in the tug-of-war with the abortionist and mother on one side and the tiny babies and lily-livered wimp on the other?
It's almost as if that bit about the vacillating boyfriend was included to illustrate the strength of her resolve and her absolute authority and autonomy.
Of course she is not married and the donor boyfriend seems like an after thought as far as any say in the matter. Maybe it's wrong to speculate about the man in this situation, but I'm guessing he is a feminized male.