Whether you're tracing the roots of your family tree or trying to determine descendent's of a family member for legal reasons, understanding the difference between lineal and collateral descendants is helpful. Lineal descendants are considered direct descendants, while collateral descendants are not.
Collateral and Lineal Descendants
Direct descendants, or lineal descendants, are the biological children and grandchildren of an ancestor. For example, you are a direct descendant of your mother, your grandmother, your great-grandmother, and on and on. Collateral descendants are not part of your direct line; they are relatives descended from a sibling of an ancestor -- such as uncles, aunts, nieces, nephews and cousins.