You are eligible for dependents benefits if both you and your former spouse have reached age 62, your marriage lasted at least ten years, and you have been divorced for at least two years. This two-year waiting period does not apply if your former spouse was already collecting retirement benefits before the divorce.
You can collect benefits as soon as your former spouse is eligible for retirement benefits. He or she does not actually have to be collecting those benefits for you to collect your dependents benefits.
If you are collecting dependents benefits on your former spouse's work record and then marry someone else, you lose your right to those benefits. You may, however, be eligible to collect dependents benefits based on your new spouse's work record. If you divorce again, you can return to collecting benefits on your first spouse's record, or on your second spouse's record if you were married for at least ten years the second time around.