He was sleeping, and then started crying loudly and a few seconds he stopped breathing, and passed on to kitty heaven. I wish you and momma cat the best with the rest of the litter. I am very afraid that when she has her babies that the older male cat will act viciously towards them, possibly hurting them. I have heard stories where tomcats kill male kittens for rival reasons. If I am right or wrong please gives some tips or ideas on how to prevent any problems.
Tomcats are un-neutered and usually feral cats.
You do not have a tomcat. But the most important thing is that you feel comfortable. Perhaps the best way to get there is to supervise visits between your male cat and momma cat. If you get to a point where you believe the kittens are going to be ok, you can allow visits to continue unsupervised. Keep me posted.