I don't think it's impossible, But I think you can have more than one. Like you could probably be completely in love and totally happy with a few different people. But which one you end up with depends on the choices you make. That's just the way I prefer to think of it :]
i do believe in soul mates, and I do believe that person has made for you by god and will be the perfect fit. and I don't think people can shape others into becoming their perfect soulmate that's only cheating yourself. and if one of them gets married I believe that fate will eventually bring them back to each other. and everything does happen for a reason.
i do believe in soulmates actually! i know that some people think that's silly, but I do! and I think that if one married another, he/she would eventually find himself/herself back to the one he/she is destined for! that's just my opinion, I'm sure many people disagree with me!