Gifts for grandchildren’s boy/girlfriends

I didn’t want to hijack the ‘Family Gifts’ thread, but I’m wondering how others have dealt with the arrival of boyfriends or girlfriends.
I give my grandchildren money and a ‘wee minding’ at Christmas, so happened to say to my son that I didn’t know what to do about grandson 1’s girlfriend, as they are renting a flat together. Son then said that if I give to her, then I can’t really not give to granddaughter’s boyfriend, as they have actually been together for longer than grandson and his girlfriend, so his suggestion was grandchildren only!
I won’t be here at Christmas, so it’s not as if we’ll all be together, but I just wondered what others have done when a ‘significant other’ comes on the scene.
My friend’s opinion was to give nothing till they are married, and that living together is no big deal nowadays!