That's almost plausible, certainly better than the official explanation,but it would make more sense with two different peoplem preferably ones who had some history of considering each other as sexual partners. In this case, we have Gwen, who was a virgin and probably wouldn't equate "providing sex" and "nurturing" that quickly, especially since the person in need of nurturing is someone she'd have normally seen as sexually inappropriate for several reasons. (It can't even be argued that she had seen Norman as a father figure and that got twisted, since "father figure" is even less appropriate than "charismatic" as a description of Norman.)
On the other hand, if you'd thrown in a "That's terrible, my dear girl. You need a drink..." scene, it'd make more sense. But they didn't do that.
Even so, it was still a bad idea. It requires the characters jumping through hoops to make it work and it doesn't serve any purpose. I think they justified it by saying that it showed Peter as heroic because he could forgive Gwen. That just goes to prove that Marvel no longer has any idea what "heroic" means. Forgiving a long-dead girlfriend for a one night stand is commendable, but nothing superhuman. She's dead and no longer a part of his life. Now, if Peter had always known about the children and had planned to help raise them as though they were his own, that would have been impressive, but I guess that would have made him too good a person.