My boyfriend had two children 1 is 16 now ( not mine ) the other is mine she’s 5 . I’m wondering if my child’s benefits will go up when her sister turns 18

Hi. The answer to your question depends on whether or not your boyfriend is living or deceased. If he's living, then your child's benefit rate will likely go up when her sister is no longer eligible for benefits, but not if he is deceased.

Children who are eligible for child benefits on the account of a living parent can be paid a maximum of 50% of the parent's primary insurance amount (PIA). However, if more than one child is eligible for benefits on the same living parent's account, then their actual payment amount is almost always lowered due to the family maximum benefit (FMB). In those cases, when one child stops getting benefits then the remaining eligible children can be paid more.

However, if your boyfriend is deceased and if only 2 children are receiving benefits from his record, then the FMB would not reduce their benefit rate. Surviving children can be paid up to the maximum of 75% of the deceased worker's PIA, and the FMB on survivor accounts is always at least 150% of the deceased worker's PIA. So, if your boyfriend is deceased then your child is probably already receiving her maximum survivor rate, meaning that her rate won't increase when her sister stops getting benefits.

Best, Jerry