I think it's something along the line of "he fell seriously in love with someone"
-> which means: the father didn't love the mother, but really loved his child!? (because the curse only disappears after the child was born)
My theory is this, the one cursed must have a child to get rid of the curse... But, I'm assuming, there might be a possible loophole to this curse. The cursed one can love anyone they desire but he or she can't be certain if their love interest actually loves them back because... You know. But if the cursed one falls in love with someone and that person actually, truly loves them back one of two things could happen... One, The curse fades into nothing since there's no one to pass the curse onto (unless it's aimlessly floating in the air until it finds its next victim) or two, the curse spreads out between the two. Meaning the curse isn't as strong anymore and its now shared with the other person.
Honestly none of this is probably true ╮(￣▽￣)╭ but it's fun to theorize!
Possible spolier
How did he get rid of his curse? Did I miss something??