I am pretty sure he resented me for most of his childhood because I was a second dad and he only saw his “real” dad every other weekend. It took a very long time of just being his dad while trying to make it clear I wasn’t replacing anyone, that he just had 2 dads. Bonding takes time. And something to invest in on a regular basis in various ways. What is your son into? Horseback riding, Hockey, Basketball, playing video games, drawing?