My wife is 4'11", I am 6' and our girlfriend is 5'10". I bought a house with four bedrooms and we each had our own room. We used my room for sex since I had the king sized bed which started out as a waterbed in the old days and finally changed to a regular mattress when waterbed stores no longer existed.
We actually enjoyed sleeping alone. We all had different bed and wake times due to our jobs. I ran a business in Hong Kong so I would get phone calls and faxes (before email days) all night long.
When we stayed at a hotel on vacation, we got two twin beds and my wife slept with her g/f and I slept alone. I do not like sleeping with one person so three is out of the question.