Some experiences can change one's personality. Everyone was born with love but along the line, some were taught hatred either by experience or people around.
I can't fathom my head round how someone would impregnate his wife's sister. However, every human has a choice; a choice to love or otherwise. I won't take that all she could offer irrespective of her experience is hatred or backstabbing. It's sad that she died before two of you could talk.