Did you notice that everyone was saying that Gabriel is hawkmoth, or hawkmoth probably is Gabriel. Well they could be right for when you colourise the photo of hawkmoth before transformed in The orgin episode part one, the person looks like Gabriel and has the same or similar clothes to Gabriel. But what if Gabriel has a twin he could be hawkmoth. Maybe they both loved Mrs Agreste and that is why she left and when hawkmoth found his miraculous he used it to try and get ladybug and cat noir's miraculous so he can bring back Mrs Agreste and make her love him. This is my theory
My top suspect is now Mr Agreste after watching the Christmas special because hawk moth appeared and Natalie said that Mr Agreste coincidence I think not