Once you and your dependents are approved for SSD benefits, you all qualify for backpay. This means that any months you were waiting to qualify for benefits should be paid to you in one lump sum.
If you were approved for benefits before your dependents, then the months you spent waiting for approval may also be paid in one lump sum to your dependents. For example, if you were approved in January, but your child or spouse did not get approved until March, you should receive a lump sum for the months of January, February and March of that same year.