Answer:
Life estate.
Step-by-step explanation:
Since the property will only be enjoyed for the rest of Ashton's life and should be passed to Andrea's (the original owner) great grandchildren, Arden and Allen, such interest is termed life estate.
Life estate is the ownership of a land and/or the property on the land for the period of the person's life, therefore it is of limited duration. This estates is terminated by the death of the owner which is then returned to the original owner or be passed to another person(s) as the case of Andrea. Also, he can let this property out for a short term but cannot sell it.