There are instances where a male child's last name is changed because the step-father adopted him.

Please use source documentation when verifying any and all names but understand that even source documentation could be wrong (such as obits where they are written by family members who may have spelled their own relative's names differently that what they were on birth certificates or families that held secrets and omitted names completely from the obit).

A lot of male descendents also carry their father's first name as well as the last. So your tree might end up having 10 James Cooley's or 20 John Cooley's. Such is the case in my own tree.

Source documentation is always your best bet.