20 C.F.R. § 226.50
There is a monthly ceiling on total family benefits which limits the amount of certain portions of the employee and spouse annuity. This railroad retirement family maximum amount varies according to the employee's earnings in the ten-year period that ends with the year in which his or her annuity begins. If the employee and spouse annuity amounts described in § 226.52 of this part are higher than the maximum from § 226.51 of this part, first the spouse tier II, then the supplemental annuity and, finally, the employee tier II are reduced until the total annuity amount is equal to the maximum or until the spouse tier II and the employee supplemental annuity and tier II have been reduced to zero, whichever comes first. The reduction for the railroad retirement family maximum is first computed from the date the employee's annuity begins. It is recomputed if the employee's tier II rate is reduced for entitlement to a vested dual benefit. It is also recomputed if a workers' compensation or other disability benefit begins or ends, or the employee's tier I benefit or supplemental annuity begins after the beginning date of the regular employee annuity. Finally, it is recomputed if a spouse who was entitled to an annuity divorces the employee or the spouse annuity entitlement ends.
20 C.F.R. §226.50