Social Security is the primary source of income for millions of retirees. But there's a lot of confusion about how divorce affects benefits for ex-spouses. With complex rules, divorced spouses need to understand the ramifications of certain decisions on their Social Security benefits.

In the following video, Dan Caplinger, The Motley Fool's director of investment planning, runs through the basics of Social Security rules governing ex-spouses. Dan points out that 10 years is the key time frame for the length of a marriage to give divorced spouses rights to claim benefits based on their ex-spouse's work history. Moreover, Dan notes that your ex-spouse's future marital status doesn't matter, but if you remarry, it can close the door to collecting benefits based on your ex-spouse's earnings. Dan concludes with some special rules governing survivors' benefits that are more lenient on those who remarry.