how do get my x husband, common law spouse to split joint custody of our childred with out any one of us on child support?

Custody and child support are two different things. You can get one and not the other - if that is your question.

Are you legally in a commonlaw marriage or is that just your thinking because of the length of time you've lived together.

A Court can decide support and/or custody. Ask for one or both.

First, any question on law needs to include your general locale as laws vary by area. Second you need to define who has primary custody now and what custody you want split. What children are there and their ages.

Is there a court order now, giving the two of you "joint custody"?

Chances are, of there is no custody decree, you each have total custody. I'm guessing that is what you mean. To answer your question, you would have to file a lawsuit against your chidrens' father to establish custody.