I wouldn't even share a room.
I'm in my mid 40s, I did my years of backpacking, sleeping in dormatories, sleeping bags on the floor, sharing a bed, in my teens and the first half of my 20s.
I don't want to any more.
I'm middle aged and I want my space and privacy. I don't want to share a bed nor even a room with my friends any more. I only share with my DH and my own kids, and tbh now the kids are older I don't share with them for more than a single night any more - 3 bedrooms now on holiday (teen DD, pre-teen boys, me and DH).
So nope. Just because I don't want to.
This actually happened in June - away with 2 female friends and they suggested a triple room room. Nope, I want my own room, and an ensuite too. I don't mind budget accommodation at all, including hostels, but I want my own space. I'd rather my own room in a cheap but clean YHA hostel than share at a 5* hotel. They shared a double, we were all happy.
You don't have to be happy with it - it's a holiday, so if you'll feel awkward or grumpy or imposed upon or uncomfortable get the booking changed. It's not an emergency arrangement, it's meant to be a break not mildly awkward.