Allen and Betty marry and have a son--Charles.
Allen and Daisy marry and have a son--Edgar.
[Have you noticed that the names are in alphabetical order, for clarity.]
Allen is the father of Charles and Edgar.
Daisy is the step-mother of Charles and the mother of Edgar.
Betty is the mother of Charles.
Is Betty the step-mother of Edgar?
Why or why not?
Thanks in advance for your opinion.