I can't find an answer to this one question so I thought I'd trouble the hivemind. It's pretty inane, but whatever. Spoilers up to fairly recent events below.

So my question is: can only God make more angels? At one point Cas encounters a girl who is the offspring of an angel and a human, and Metatron tells him that she's an "abomination." Okay, fair enough. But can two angels have an angel baby together?

These days have been hard for angels. A lot of them have been dying. Is there any way of making more of them, or have their numbers been slowly declining since God left? I mainly just wonder if you could potentially end up with dwindling numbers of angels and ever-increasing numbers of demons.