Backstories are always fun!
Slight correction, Fizz was just Blitz´s friend, not his brother.
We can definitely see why Blitz is so messed up as an adult, his family life sucked. And even if he started things with Stolas out of pity, they kept going, I mean, technically it was to keep access to the book, but I feel like it´s obvious he still cares about Stolas, in his own complicated way.