Johannes_P t1_jee8nlc wrote on March 31, 2023 at 11:40 AM

Reply to comment by CornFedIABoy in TIL in order to prevent certain legal instruments from operating in perpetuity, a Royal Lives Clause may be written into a contract which provides a definite but extended period of time usually tied to twenty-one years past the death of last living descendent of the current British monarch. by AudibleNod

From the Wikipedia article, it seems the Rockefellers are also used.

But royal families have the benefits of officially recorded lineages ensuring no ambiguities about descendents and good living conditions and healthcare ensuring long lives.