Disability Benefits: SSDI Dependent Benefit Backpay

Hello. I recently (August of 2014) became aware that the father of my two children, whom I have not spoken to in many years, was receiving disability benefits, and I was told that my children may be entitled to benefits as well. I contacted SSDI, had a phone interview, and was approved in January of 2015. When I had the initial interview, the case worker told me that my childrens' father had "protected" them on his claim, and that they were entitled to benefits starting in June 2010, and he went on to tell me the dollar amount they should receive. However, when my award letter finally came, it stated that they would only be receiving backpay benefits for the year prior to when I had initially applied for benefits.

This is upsetting, understandably, and I am wondering if I should attempt to contest this decision? Or is this the normal procedure for someone in my situation? Any help is appreciated.

Disability Benefits: SSDI Dependent Benefit Backpay