I receive SSDI, and I have 2 children that receive benefits on my behalf. Can you tell me when one of my children's benefits end at their age of 18, will the other child's benefits increase?
In your case, yes. Child's benefits payable on the record of a living parent are normally payable at a rate of 50% of the parent's primary insurance amount (PIA). A person's PIA is equal to their full Social Security disability (SSDI) benefit rate, or their Social Security retirement benefit rate if they start drawing at full retirement age (FRA). However, there is a family maximum benefit (FMB) that can be paid on any person's Social Security record, and that can cause the benefit amount payable to eligible family members to be reduced.
The maximum FMB that can be payable on the record of a worker receiving SSDI is 150% of their PIA. So, for example, if a worker's full SSDI rate (PIA) is $1600, the FMB on their record would be limited to $2400. That leaves $800 to potentially be paid to eligible family members. Since child's benefits are calculated based on 50% of the living parent's PIA, if only a single child was eligible for benefits in this example the child would get their full benefit amount of $800. However, if 2 children were eligible they'd have to split the $800 available from the FMB and receive $400 each.
Therefore, when your oldest child is no longer eligible for benefits your youngest child's benefit rate will likely double, leaving the same total amount of benefits payable.