I'll do the main characters that have/had a relationship with their parents!
Mina: Considering she risked her life to escape to return back home to her family, she obviously loves her parents very much, and they love her equally back. Their relationship was really good, and Mina misses them more than anything.
Fletcher: His relationship with his mom was also very good! His mom was extremely nurturing towards him and protected him until Apollo (his boyfriend) came into the picture. He never had a relationship with his father, considering Fletcher and his mother immigrated after he was born, and his father stayed in their homeland.
Apollo: Apollo's relationship with his parents was very shaky. His father essentially hated who he was, as Apollo wasn't as strong or ruthless as the other leodins. They got into both verbal and physical fights often, and it only increased once Apollo's mother passed. Apollo loved his mother, as she saw him for him, and knew that he would need help. Apollo's mother protected him from his father and other leodins that would bully him, but she got sick and passed in Apollo's arms.
I haven't really expanded upon Anne or Moss's relationship with their parents, and Azrael (the main antagonist)'s relationship with his parents has some pretty big spoilers in it, so I can't really say much about his 
