My rats suddenly turned aggressive

Question
I have a 2 year old male rat, who used to have a 3 year old brother who recently passed away on us. A week after his paassing i thought it would be a good idea to get a new friend for him. I ended up with two male baby rats. i was introducing everyone slowly in the bathtube everyday, and things seemed to be doing okay. Once i tried introducing the babies into the adult males cage, my adult got angry, he was biting the babies, he even bit me three times that night while i was removing them from his cage. ever since then, he bites me when he feels like it ands they always make me bleed. sometimes he can be a sweet boy, but why has he all of a sudden started biting me? he never used to do this when the other rat was still alive

Answer
Your boy isnt suddenly aggressive.  He lost his  cage mate, which causes stress from mourning. You bring in two baby rats (adult males loathe baby rats)  How long were the babies in quarantine for before they were introduced to him and how long did their cage sit next to his, making their prescence known, and how long was he introduced to their scent on you before he was put together with the pups?

It seems introductions were not done gradual and he has not had a chance to get used to them. Not only that, but they are baby rats and most male rats do not like baby rats. He smells the other rats on you and this is why he is biting you.

You need to wait for the pups go get older for starters, but for now, keep them apart and when you handle the older male, be sure you do not have the young rats scent on  you or this will provoke him to bite.  He is showing you that he is protecting his territory from intruders.