Before Gray was released Pete said that it wasn’t a memoir and that the characters in it were only loosely “based” on the people in his life. What we all assume (it’s pretty obvious) is Patrick’s character is the narrator’s friend and band mate, Martin. I don’t have a copy of the book and I don’t really want to spoil anything anyway but he talks about writing with Martin and having a lot of faith in him and knowing that if something happened to him (the narrator), Martin could continue what they started together without him. He also describes Martin as being very polite and having kind eyes and an infectious smile. At some point in the book, he develops a fear of flying and panics in an airport and Martin helps him calm down and even goes as far as too helping him untie/tie his shoes and take them off, etc. 

Even if you wanted to argue with any of those things being very Patrick/Peterick, you can’t deny that Martin is Patrick. It’s his middle name after all.