Below comment is for those who have seen the drama:
I don't think they ever implied that Xiao Qi was his son, he just reminded a bit of him. Since the beginning he had said that a father would recognise his child immediately. Moreover through the drama I felt that Doudou could be the stater boy, Xiao Qi's friend who died because he really looked like the ML...
The writers must be held accountable!... I will cherish the first 11 eps... because after that.. chaos! Even if they wanted to point out the psychological traumas at the end they made him dumb! This is not the same! They should have kept the script within the context of the first eps. As for Sa Xin character... totally meaningless!