That's a complicated situation...
...particularly if one person wants it and the other doesn't--or even isn't sure whether they do or not. Personally, I'm with you. I don't commit easily, but when I do, I'm fully committed and expect him to be too. Sharing is definitely a no. But on a purely fantasy level, the idea of it is absolutely hot. I love to fantasize about being with all sorts of group-orientated activities.