Need advice from Step Fathers/Fathers please

Two things.

Be firm but fair.

And.

You cannot be a good parent and a best friend too. One or the other.

I know a lot of people may disagree but over the years raising kids and step kids (a term I despise) you really have to be a parent first and foremost.

This is not to be confused with you can't hangout and have a blast with them, because you can.