It IS normal for a person to be required to use their SSDI back pay to reimburse a long term disability insurance provider. I am not aware of any cases where the LTD company has also demanded to be reimbursed the children's portion of the SS back pay. However, if the monthly amount of your LTD payments included an extra amount because you had dependent children, it could be valid for them to demand the children's share as well.
At this point, I really think that you are going to have to hire an attorney to deal with the LTD company. Are you supposed to be continuing to receive a reduced LTD benefit along with your SSDI, or does your SSDI completely replace your LTD benefit?

