It is not done in an obviously jokey way. I suspect they are being serious, albeit in a completely ignorant, unthinking way.
This is a young teenager, ie under 16.
Not my child, so therefore nothing to do with me, and I'm expecting to be told IABU in concerning myself with it.
(If it was my DC though, I would be making them delete it immediately. And possibly banning from FB at least temporarily).