Complex sentence: The first residents of what eventually became Tarrytown were the Native American Weckquaesgeek tribe, who were closely related to the Wappinger Confederacy and further related to the Mohicans.
Split into simpler sentences: The first residents of what eventually became Tarrytown were the Native American Weckquasgeek tribe. The Weckquasgeeks were closely related to the Wappinger Confederacy and further related to the Mohicans.