My housemate has moved her boyfriend in? In desperate need of advice please?

We live in a 4 bedroom house with all the rooms occupied, 3 of the rooms being able to fit a double bed. So my housemate has moved her boyfriend in, he has been living here since the first day we moved in and now 4 months later agreed to contribute to utilities. There will be no back log of payment. My house mates are also my friends as we attend the same university and are on the same course. Do you think we should be making him pay an equal share of the rent too as he shares my housemate's room? Or is that unfair with utilities being enough? Thank you