The term 'primogeniture beneficiary' refers to a person who is the recipient of an inheritance or other benefit due to being the ELDEST SON. The crossword solutions for this term are SON (3 letters) and ELDEST (6 letters). Primogeniture is a system of inheritance in which the ELDEST SON receives the majority of the family's wealth or property upon the death of the parent. This system has been used in many cultures throughout history, and is still practiced in some parts of the world today.