Final answer:
The grandchildren will not receive Blackacre until they reach the age of 25, which is older than one month.
Step-by-step explanation:
The statement is False. According to the given information, O has a one-month-old child, but in order for the grandchildren to receive Blackacre, they must reach the age of 25. Therefore, O's grandchildren would not receive Blackacre until they reach the age of 25, which is older than one month.