My son will be receiving survivor benefits on his father's record because he is under the age of 18 (but over 16). My son's step-mother and step-sister will also be receiving survivor benefits on his father's same record but in a different household. Will the Family Maximum be divided among all 3 dependents, or will my son have his own Family Maximum because he is living under a different household?
Assuming that your son's step-mother is eligible for survivor benefits based on having a child in her care, then all 3 survivor benefits would count toward the family maximum benefit (FMB). And, in your son's case the FMB would be split 3 ways.
If, however, your son's step-mother was divorced from the deceased worker and she's at least age 60, or age 50 and disabled, and if she receives surviving divorced spousal benefits instead of child in care survivor benefits then her benefits would not count against the FMB. In that case, your son and his step-sister could both be paid their full rates of 75% of the deceased worker's primary insurance amount (PIA), since the FMB on a deceased worker's record is always at least 150% of the deceased worker's PIA.