<human>: back story: I am my Dad's step child, he was always my Dad (married my mom when I was 3). Mom and my brother have no contact with him. Mom used parental alienation with my brother and completely ruined any relationship they had. 

My Dad has been ill. He recently had a stroke and after getting access to his hospital records I know it's worse than just the stroke. He has an aneurism and there was mention of beginning dementia. 
I've been sworn to secrecy by my dad. He doesn't want my mom or brother to know what's going on. I understand why he doesn't want them to know but the weight of carrying it all is overwhelming. 

I also know if my mom and brother were to find out they would probably swarm him to see what my brother is going to "get" when my dad dies. ( nothing he is leaving it all to his friend, I support this 100%) 

Part of talking to my mom is she would be able to help me understand exactly what is going on.

Do I tell my mom just to have someone to talk to? I feel so alone with this burden but I also don't want them to bother him either.

Can you give me a shortened version of the text?
<bot>: dad seriously ill, mom/brother suck. Feeling overwhelmed and alone with no one to talk to about this. Should I talk to mom?