This is normal between two males. Sometimes they need their own space and sometimes they need cuddles.
Once I rescued two males from Montreal... The himi was constantly being bullied by his brother and he would scream and hide and the whole bit. I was getting very frustrated and was going to have both rats neutered. Then one night I decided to hide and watch them. What I saw was the himi going up the ladder to the level on top of his brother, then he would jump down on top of his brother. The brother would then grab the himi and flip him. The himi would scream and freak out and the whole bit and run away... then I saw him go back up the ladder, wait for the right time and jump down on his brother again. Pascal would then turn around and flip the himi until he squealed like a pig... they were playing! The himi wanted to be flilpped and tickled.. that was the game.
What you could do is give them more out time, maybe start taking them out one on one for some cuddle time with you. Change up the cage once in awhile by adding a new chew toy or new box or something... keep them busy mentally and physically.