Census Issue or Family Issue?

Hello,

This is my first time using the community part of Familysearch, so I hope I'm in the right place. So here it is:

According to the 1910 census, then 21-year old Bennie Freeman(G7J3-W4F)'s father was a 44-year old Will Alexander(G8R5-RXN). Not only does Bennie not have his father's last name, but Alexander's wife, Leola, was 30 at the time of the census, and therefore probably not Freeman's mother.

Is this an error in the census' data, because the rest of Alexander's children(aged between 4-8), have his surname? The only real life situation I can come up with that could explain this is that Bennie was a step-son from a past marriage of Alexander's.

The source page of Alexander & his family: https://www.familysearch.org/ark:/61903/1:1:MKV8-TVH

If there's somewhere else better suited for a question like this, please direct me there. Thanks,