Hi...my step daughter and her sister both get death benefits from their mother passing her sister turned 18 in october will my step daughters benefits go up??
The only reason that your stepdaughter's benefit rate might increase as a result of her sister's benefits stopping is if your stepdaughter has been receiving a reduced rate due to the family maximum benefit (FMB) payable on her mother's record. But, if only 2 children and no surviving spouse have been drawing survivor benefits on the account of your stepdaughter's mother, then it's unlikely that your step-daughter's benefit rate would increase when her sister stops drawing benefits.
The maximum benefit rate that can be paid to a child eligible for benefits on a deceased parent's record is 75% of the parent's primary insurance amount (PIA). The FMB limit on a deceased person's account is always at least 150% of their PIA, so if only 2 children are receiving survivor benefits on a parent's record they can both be paid their full 75% of the parent's PIA without exceeding the FMB. Thus, your stepdaughter's benefit rate wouldn't increase as a result of her sister's benefits stopping unless more than just those 2 children have been drawing benefits on their mother's record.