Looking for a poly romance I can’t remember the name of

Hi everyone, so I’m trying to find a book I read a while back. Here are the details I remember:

One main character is an artist. Before he became an artist, he almost ended up a prostitute, but killed the person he was supposed to be servicing or just knocked him out. Don't completely remember, but I do remember that he was able to get away.

At one point, the artist witnesses a girl being either killed or injured. Later he finds out that girl was actually the sister of another main character.

That brother is a soldier (just returned from the military), and I think his name started with C. He comes home looking for his sister, and the artist was the last one who saw her.

There’s a third guy in the mix named Max, I don't remember anything about max, just that he's had some past trauma.

The three of them — the artist, Max, and the soldier — end up in a polyamorous relationship (MMM).

I do know that I read it online.

Does anyone recognize this? Even partial matches would help. Thanks!