"So, is the step brother or step sister also called a sibling?"
"No!" I said instantly.
But that was a brilliant question!!!!
"Any way some step brothers or sisters could be close and could have been brought up together and may feel like siblings."
Over the one hour we were on line, we did a lot of other work, but towards the end of the class his question kept niggling my battered brain. So I looked it up on line and found something to tell him
A step brother or sister is called a half sibling.
A logical lawyer in the making...that kid!!!