I'm not sure about this. It seems from a quick google that this is verging on a bit late.
My others were well up and about by this time, and ds1 walked just before 10mo.
Ds3 isn't even holding himself up on all fours - he can just about roll, but hardly does it, and he cannot make his way across the room at all - he wants to stand up and is pulling himself up on his knees, sort of thing, by holding onto the chairs/my legs etc but no sign of crawling.
I wondered if it is to do with his tummy muscles as he seems to have a diastasis, and I don't know if that affects this sort of thing?
Should I see the HV or the GP about it? Or neither? he is happy otherwise.