Is OTHER wrong in the post ? POST : So my parents are divorced and i always knew that eventually they would find new partners and move on. I already know my dad has a girlfriend . 

The thing comes this day  when we were having lunch together and i thought he was going to give me the news that her girlfriend was pregnant BUT the real suprise comes to my like a slap when he says 'you have a new little brother he was born a mont ago'
Instantly in that moment i felt rage but now i don't know if i was really allowed to?
Im still furious and i don't think i will be able to calm down at least for a while.
 
But do i have a right to be angry or AITA? 

Have in mind that he is really manipulative and he started sobbing while telling me this, i used to fell for that when i was younger but now im more immune. 