We are going to Rome next week and are staying at a Marriott. I know that their rooms are either 1 queen/king bed or 2 twins. We are a family of four, so we had to upgrade to a suite.
I used PL for some other travel to Venice/Florence/Milan. We had to buy two rooms and then I call the hotels and ask for connecting rooms. Most Euro rooms are just too small for two adults and two kids. I would find it too crowded with three adults.