Final answer:
The property interest described in the question where Tom Jr. can retain property as long as he remains unmarried is known as a qualified fee. This type of estate ends upon the occurrence of a specified condition such as marriage, distinguishing it from a fee simple absolute or a life estate.
Step-by-step explanation:
The question relates to the classification of estates in property law, specifically describing a scenario where Tom Jr. can keep the property transferred by his parents for as long as he remains unmarried. The correct term for this scenario would be a qualified fee, also known as a defeasible fee. This type of estate is characterized by a grant that contains a condition which, if violated, can cause the transfer of the property to someone else or back to the original owner. A fee simple absolute is the most complete ownership interest one can have in real property, with no conditions attached.
A life estate grants ownership rights for the duration of someone's life, typically the life tenant's, and cannot be bequeathed to heirs. A fee on condition is similar to a qualified fee but typically involves a reversion of the property back to the original owner upon the occurrence of a specified event. The scenario described does not match a fee simple absolute since it ends if Tom Jr. marries, nor does it match a life estate as it doesn't end with a person's death but rather a change in marital status. Therefore, a qualified fee most accurately reflects the condition provided in the original question.