I am father of two kids (16yo, 13yo), I have not been with the mother for 8 yrs (never married). We have had a "flexible" arrangement with the custody of the kids for this time. They spend most of their time at their mom's, I spend many weekdays at the mom's house with the kids. I am no longer interested in continuing this arrangement. I want to have my kids with my 1/2 time. What obstacles will I face?