I get why you are upset, but it is not like he woke up one day and decided to love her knowing she was a relative. He loved her before finding out these "circumstances" and was wishing for afterlife. Let's say it was a bad turn of events or that Fate was playing tricks. I don't fault him too harshly.
Nah he was nasty to her every second he could get. I fault him incredibly harshly, there's a way to treat a person, and that's with respect. Especially for someone who loved him so dearly but he was too self centered and self pitying, hence not caring about anyone else's feelings. He had no growth from childhood to adulthood. Just a whiny, childish asshole with no redeeming qualities. It is a bit pitiful how the og fl doesn't care an ounce for him any longer but tbh one reaps what they sow.
"Alas, I have lost something so terribly lovely." NOW YOU'VE JUST REALISED WHAT A FUCKING ASSHOLE. Fucking bastard I hope he regrets even being born.