Quote Originally Posted by Kraco
It's not like being a happy husband and a loving father would have changed his past, in fact it would have only made him a massmurderer and nothing more if he hadn't been ready to see the road till the very end.
Quite the opposite, actually.

Kirei asked Kiritsugu why he didn't obtain the grail after all the work he's put in, and Kiritsugu said that the cost outweighs the benefit. Kiritsugu saw that there's no point in walking down his road till the end anymore because the end isn't what he had hoped it would be (his miracle). Any further benefits couldn't make up for the cost he'd have to pay, so he just stopped in his tracks.

At this moment in time, Kiritsugu is just a mass murderer because he ended up killing for nothing.

Quote Originally Posted by Ryll
Wasn't there a scene where Kirei had to convince Gilgamesh that the Grail was worth having? Something new finally worth adding to his collection?

It wasn't a matter of making him realize it was already his, Gilgamesh seemed to understand that the Grail was created after he could have possibly ever owned it. He is a few millennia old, while the Grail is only a few hundreds of years old. Kirei had to convince Gilgamesh that it was something he should bother himself with.
I can't recall the scene, but if it did happen then it could work..