The term 'FIRST BORN' refers to the first child born in a family. The crossword solutions for this term are CAIN (4 letters), ELDEST (6 letters), OLDEST (6 letters), and SENIOR (6 letters). All of these words refer to the same concept, that of being the first born in a family. CAIN is a biblical reference to the first son of Adam and Eve, while ELDEST, OLDEST, and SENIOR all refer to the same concept of being the first born in a family.