I have never personally been in love with two people at the same time, but I do not assume it is necessarily bad if someone would find themselves in that position. I think it is far more likely to be in lust with two different people, rather than in love.
Sure, we love our kids and our friends, our partners and our siblings. We're always loving more than one person at a time. If we are talking romance, though, it gets complicated, and very few people can pull it off because most of the time--unless it is a conscious philosophy--one of the two or three is going to get too jealous to continue.