My father passed away in Feb 2018 at age 67. He started Social Security as a disability benefit. When my mom turn full retirement age, she started collecting a spousal benefit and is now collecting a widow's benefit. My mom is 67 and plans to delay her own benefit until age 70. My brother has Schizophrenia and was disabled before age 22. However, brother is currently collect SSI and SDI on his own record. I want to know if and how my mom can let my brother collect Social Security under her record. Social Security told my mom she could reapply for my brother since they did not have in their records that his was disabled before age 22. But we are't sure if there is still away for my mom to continue to delay her benefit while having my brother collect on her record. As a side note, it makes no sense for my brother to collect on my dad's record as his was very small and the family maximum would reduce my mom's widow benefit.
I'm sorry for your loss.
Your brother couldn't collect disabled adult child's benefits on your mother's record, at least while she's still living, until she starts drawing her own benefits. And, if your mother starts drawing her own retirement benefits now, she will stop accruing the 8% annual increase from delayed retirement credits (https://www.ssa.gov/planners/retire/delayret.html) that she would otherwise receive if she waited until age 70 to switch to her own record.
Your mother may want to consider using our maximization software to compare her options in order to determine her best overall filing strategy.