At first I found it awkward that DS1s gf was here a lot but to be fair he goes to hers a lot as well, same with DS 2
And there is lies the difference between your situation and the OPs - her daughter an her boyfriend don't go to his house a lot.
Yes I guess but I should have added that there is ALWAYS one of the GF here. DS2 goes to his gf parents in the weeks and she is here at weekends. DS 2 usually has gf here mid week and he often goes there at the weekend.
However everyone is here at the moment!!
I don't think sharing expierence stuff is having a go at OP, just showing different perspectives, coping strategies etc. As I said I know mine won't be here for ever and to be honest, you never know what's around the corner ( good and bad) so I like to have family close by and happy.
I'm not sure why OP can't say,' Oi you two , bugger off for the weekend'. ( go camping, go for a city break , anything) mine often go to Edinburgh for a weekend and book a cheap break in a Premier Inn or something if it gets too much.
If they get lippy a short rebuke won't kill them!