Can Reliance Standard use my son's benefits as offset after the initial offset for SSDI?

I have been receiving ltd benefits from reliance standard since 2007. I was pretty much forced to file for social security which offset their payment, I quickly paid back the overpayment. They tried to offset my VA benefits but after 6 months of non payment and hiring a lawyer they conceded and continued paying. Then in 2010 my son was born. I was not aware I was due any additional social security benefits until reliance standard told me to file for them. They used my sons benefits as yet another offset. Can they do this after the initial offset has been made? My policy states that after the initial social security offset they can not offset any more due to any cost of living increase. Having a child definatly increased my cost of living expenses. He was born 3 years after the initial offset.