The term 'Family Tree Branches' refers to the members of a family and their relationships. The two crossword solutions, KIN (3 letters) and SONS (4 letters), refer to the people in a family who are related by blood or marriage. KIN is a general term for relatives, while SONS specifically refers to male offspring. Together, these two words represent the branches of a family tree, which can be used to trace the lineage of a family.