Are soulmates real?
what is your definition of a soulmate?
What's your definition of a soul? If you subscribe to the traditional monotheistic viewpoint, than you probably don't believe in reincarnation (although, personally, I think that reincarnation fits in very well with a monotheistic god. Like tests in class, the various lives would prepare you for the final exam).
If, instead, you subscribe to a larger idea of karmic justice, then this question has already been wonderfully answered.
If, however, you are a one-life monotheistic believer, than first you must ask what your perameter's of a soul mate are. Is it one person, who is perfectly matched to you in every way, that you do not feel you could be complete without?
If that is your definition of a soulmate, then no. I'm fairly certain soulmates do not exist. Human beings are amazingly adaptive. The death of a loved one can hurt us, tear us apart - yet we go on. We do not forget, but we recover, continue with our lives, and even thrive.
If a spouse dies, it is more than likely that their widow/widower will remarry. This does not mean that you didn't love them, it just means you have a great capacity for love. There are some who will not remarry, but it isn't because they don't have the capacity and ability to love again; often they choose to sanctify the memory of the lost one and term them "their soulmate".
Perhaps I am too pragmatic at it all. But then, I feel that love is grown out of a match of personalities, mutual attraction, and a willingness to work together as a united team rather than some higher emotion that descends upon us when we meet our "one true love".