I would suggest giving the pregnant cat a place of her own to rest and be comfortable, even a bathroom or a bedroom away from him may work. The two-year-old male is still pretty young. Did he recently get neutered? The hormones may still be working themselves out. After your female cat has her kittens, I suggest making sure everyone is spayed and neutered. This will likely cut down on the tension, and also help control the surplus pet population.