Oh, that doesn't matter. Any god will do, as long as someone can prove to me that they are real. You see, I'm a very spiritual person, so having faith means a lot to me. I just need to find a faith worthy of my faith.
Brother Cain is a Servant of the Mushroom Cloud who has had second thoughts about blowing himself up for the glory of Titan. Instead, he wants to travel the world in hopes of finding a god with a better retirement plan.
This character is a party member.
This character has other interactions.
If you visit the bar in Rail Nomads with Corran Cain and Scotchmo in your party they will have a small dialog about worshiping booze.
Corran will appear at the Temple of Titan after completing the Titan quest arc by disarming the nuke in Silo 7. The chaos wrought by the act and the subsequent eradication of the other Servants of the Mushroom Cloud at the hands of raiders and the Diamondback Militia broke his faith.
If retained until the endgame, Corran will volunteer to detonate the nuke. The Great Glow welcomes the prodigal son as if he never left.