I don't know but maybe he knows Hwa is pretty capable by himself so he doesn't want to bother with him, considering he's a vampire too (Yibin) so he would feel more bothered. I just hope he really does love him / loved him when he was a kid and a baby
http://www.mangago.zone/read-manga/blood_link/uu/mpn_chapter-2321532/pg-5/
Um what the fuck? Is he serious?? What an asshole. So all those dad son moments were all just acting on his part?