Those are the relatives who are not part of direct lineage, but of the same ancestral line. Such ancestors would be the uncles, aunts, granduncles, second cousins and in-laws of the family. When completing a family tree it is the direct lineage that is recorded, such as parents, grandparents, great parents, etc.A direct family tree will not show those collateral lines, but they are still very important in the family history.hose are the relatives who are not part of direct lineage, but of the same ancestral line. Such ancestors would be the uncles, aunts, granduncles, second cousins and in-laws of the family. When completing a family tree it is the direct lineage that is recorded, such as parents, grandparents, great parents, etc.