What the MC sees them as and how they see him as are two different things tho. He sees them as his children but they never saw him as a father. Kinda Yutia's fault tbh but they only ever saw him as a savior/benefactor that saved them from their predicament for his own ulterior motives (which is true but not in what they think). Doesn't change that it's weird but it's whatever imo so long as the MC doesn't entertain it.
Mc to them.is the same age, he's a possessor that saw them as children that needed help, it's not like he's actually seeing them as his children. He never even went to visit them at the orphanage. So it's mostly "I raised on my back" like how older brother would raise a younger sibling as if they are a parent. I can't support the harem or any romantic relationship unless we see mc break out of that mentality. Because of it stays it's just bullshit

Deadass so odd his so called children wanna marry him like i would kinda undertsand if it was like established he sees them as his friends or something along those lines but he sees them as his kids