<human>: I'm typing this shaking right now, so bear with me.

My best friend of my entire life, birth to now, just called me to say his mom left his dad. But it isn't that simple, as in a regular divorce.

His mom has a very obscure mental disorder, an offshoot of bipolar and schizophrenia. The medication she takes restricts her episodes to occurring every few years and they change each time. We think this is one of them, she was having some physical symptoms, but nothing we could point to. She flat out left his dad, but I don't have all the reasons now.

The plot thickens, as they have 3 sons. The youngest my friend, is 18. The other 22, another 25. The 25 year old has the same disorder as his mom, and is at home recovering from the first episode he had, triggered by a separate family issue. It is very much so within the realm of possibility that my friend has the same disorder, and I'm worried for his mental health. 

He's expressed that he is distraught over the leaving, but feels mentally normal. I need to know how to help him. I guess that the best course of action would to not speculate on the disorder and help with the issue at hand, the grief of his parents splitting. Could somebody with experience in helping people, or dealing with divorce, please help me? I don't know what to say to him. Please, anybody, with anything help me. He's my best friend and it's killing me to see him like this.

Shit, I started crying now... Dammit.

Can you give me the gist of the text in a nutshell?
<bot>: read the whole thing, it's important. Friend's mom abruptly left his dad, friend may have rare mental disorder. I need advice on helping him with grief in this.