Contingent Beneficiaries (CB's) (usually grandchildren) are those designated to receive distributions only upon a contingent event - which is a PB not surviving the Client (or Client's spouse).  In such case, the designated CB would instead receive the deceased PB's share.

If a PB predeceases the Client (or the last spouse to die) and the Client has not identified a CB to receive a particular PB's portion in the event that PB does not survive the Client, then that portion of the estate will likely be probated.  In actuality, that non-placed allocation would become part of the probate estate of the deceased PB - unless that PB had his own living trust in place.