When the guy don't want to even be around his childs life

If he used to be there every step for your child also including his own. And talk about how much he loves his kids and want to spend every moment and beach days with his kids/kid. Then all of a sudden the kid/s irratate him, he starts to not pay attention to the kid/s, start geting irratated with the kids. Is coz he either was reminasing of the days when he didn't have kids and miss it or he is cheating and so that's where all his attention is going and he feels much beter with the other person because he don't have to deal with his real responsibilty's at home and so when he comes back home he gets irratated coz he has to go back an live with responsibilty's. Sorry that jus what I feel and is noticing with my son's father and soon to-b x-boyfriend.