Propositus - English meaning

noun

A person from whom a line of descent is derived; an individual from whom family relationships are calculated or on whom a genealogy or pedigree is based.

noun

The person whose entitlement, status, etc., is the subject of a given legal process; especially the testator or other person the devolution of whose property has to be determined.

noun

The first member of a family to be diagnosed with a hereditary disease or trait; the individual with whom the investigation of a family for an inherited disorder or trait begins.