My children stay with me every Friday to Sunday and one day in the week, there mother doesn't have a problem with me having joint custody. How do I go about getting joint custody.

First, its not a good idea to piggyback your question on another thread. Since this can cause confusion I've moved your question to its own thread.

What makes you think you don't have joint custody? Are you on their birth certificates? Is the Visitation court ordered? Has there been any court action?

Also, any question on law needs to include your general local as laws vary by area.