SSDI back pay for child.

I have a child who receives SSI and does not live with me. I was approved for ssdi and the family maximum will be offset by the amount my child receives now.

My lawyer said i will receive x amount of dollars in back pay. He said my child who does not live with me will receive x amount of dollars in back pay for the family max.
My question is this..
will my child (caregiver) receive the lump sum back pay for his portion? or will SSI take it all? I already know the x amount of dollars he receives a month will offset his ssi payments, im wondering about the back pay.