16yo DS has a girlfriend - she's nearly 17.
They started seeing each other just after GCSE's finished, so did spend a lot of time together after exams while DH and I were at work.
He now wants her to stay over one night next week. From what I can tell her parents don't mind (he wanted her to come home with us after the prom, but we said no - her parent was waiting for her in the car park, and apparently they'd said OK)
DH will want to fully interview her father first- I'm only semi joking. (We said no to DS1s girlfriend staying over when they were both 19 because she was from an incredibly strict religious family and DH didn't want to disrespect her father)
I've no idea what other people agree to.