I'm pretty sure Aaron is no longer involved. He wasn't on any of The Quiet Life if I remember correctly. Stephen does Anchor & Braille with a guy named Micah Tawlks now.
Yeah, Aaron was only involved with Felt. Dave Elkins from Mae was supposed to produce The Quiet Life, but the budget fell through, so Stephen and Micah did it themselves. Looks like Micah also has some co-writes on Lowborn, so I wouldn't be surprised if they collaborated on both Anberlin and A&B simultaneously. (That said, Micah's been Stephen's songwriting partner in A&B since the beginning; they were touring together and playing material from Felt before the album was even released.)