Yes I think so too.. my theory is that they were attacked by another group because of their association with the red haired dad and that’s also why he took their kid and raised him. They were his friends I think so he felt like it was his responsibility to take care of their child after their death. But there is definitely more to the story than what we know so far!
Precisely my thought ~
It was mentioned it is demon sect tradition to kill the family of and and kidnap the future heir... so I can see where all this confusion in the world is. It might have been his only way to protect their son from something, or maybe he thought taking their son as heir would be the only way he could keep them close to him. It could have also been just straight up murder for a powerful heir, because he probably had no real concept of family at the time -he probably went through the same thing to become leader- he’s only learning the value of family now.
Hmm... do you perhaps remember what chapter it was mentioned? I think I may have missed it or not fully understood it well.
It was the chapter when the demon sect was opened and the new people arrived, she mentioned something that made the leader think about their tradition for the heir to never have a father because they kidnap them after killing their family. But no, I don’t remember specifically which one that was, sorry!
Okay so the dad said "Everyone who was close to me died a miserable death" and the ML's parents (looks like) was shown in that certain panel. So, like some people are, I believe there is more to the story of why the ML's parents died and don't think the FL's dad did it. Because if killing the ML's entire family was his goal, then he woudn't take him and appoint him as the sect's heir, would he? It just doesn't make sense.