Final answer:
The issue relates to a legal concept known as a 'contingent remainder,' where G's will specifies that the grandchildren must reach the age of 21 to inherit the land.
Step-by-step explanation:
The passage in question refers to a legal situation where G devises land to his grandchildren with the condition that they must survive to age 21. This is a matter of inheritance law, which often involves stipulations set by the grantor regarding how and when their assets are to be distributed. In legal terms, this is known as a 'contingent remainder' because the grandchildren's right to inherit the property is contingent upon them reaching the age of majority, which is typically 21 years old. The clause 'to my grandchildren who live to age 21' suggests that G wanted to ensure that the beneficiaries have reached a level of maturity and are likely to use the inheritance responsibly.