Is it possible to be 'in love' with more than one person?

Yes I think you can certainly "love" many people at a time but I don't really see how one can be "in love" with more than one.
The way I seen it, Sam and Steven were very much in love..Sam was battling with sexuality issues and he thought he would be more accepted to bring a woman into the relationship and Stephen just loved him so much that he wanted him to be happy and went along with it.
Samantha came along and they loved and respected her very much as a friend and I think she was also in love with Sam so also went along with their 3some of a relationship. She also probably felt good to be taken care of by not 1, but 2 men.
It seemed to me like they were all playing make believe in a way and living in little fantasy worlds in their minds....I definately don't think they were ALL "in love" with eachother.