It seems like author changed her story. Ok if everything was black hair's plan all along why silver hair acted cold towards FL? Before everything happened this was the main problem. Also in black hair's thoughs we learnt he wanted FL happy and that's why he accepted her marriage and then when she was dead he was angry because even tho he let go of her she became miserable. That's why he wanted to change future. BUT all of a sudden everything was his plan? Nope i'm not buying it. He is crazy yes but still.
bruh why this japan dude doesn't consider other twin as his son? are they not blood related?
No they are not blood related. Only the elder twin was acknowledged as son if I remember correctly.