Although Gisela didn't have a hellish life like Leon knew, one was also weak when they met. Leon was the type who wanted to be the shield who would protect the ones he loved, but that Leon wasn't crazy enough to think that they shouldn't train and improve themselves.
Weirdly enough, Sasha, Betty, and Gisela had similar fighting styles to the ones Leon knew. Also, weirdly enough, he was by far the best mage of a group of thousands of survivors. Maybe that was why he got ahead of himself and decided to marry three times. That being said, Leon would be lying if he says that he wasn't jealous of that Leon.