I have a brown robed librarian, and a brown robed (no apron) armorer in my village.

The world was created in 15.7 or 15.6, I moved some villagers from a nearby village to my artificial village which is part of an iron golem farm. I have no idea whether these villagers were moved or just bred here.

This issue is possibly related to (or same as?) MCPE-17928.

I could share my world backup, but it is 380MB large, so I'll have to link it. If you want it, please mark this issue private.