Friends with the "ex"...are you?

Ok so here is my question of the day: Friends with the "ex", do you lie about it or are you open with your current s/o? 

So, I have been feeling like who decides who your friends with? Like, if you and your ex are still friends, do you tell you new s/o? What if they are insecure about you? Do you "protect" them by making them think you are not friends or even amicable? What if you and the ex have kids together? Does the new s/o, on both ends, get a say in your "relationship status" with the ex when you guys have kids together? Is there a line that is drawn?

I think most people are uncomfortable with their s/o being friends with their exes. I know that I have had this issue but more along the lines of, this is the woman who you cheated with, she can't be a friend. But does the "new" s/o get to say the same, if they cheated on you with their ex? What if there are kids involved? How do you trust the situation? Do you forbid him/her from being friends with them, though you know they have kids together? Or does he/she make you feel comfortable and tells you, "we don't even talk. all we do is fight. If it wasn't for the kids, we'd never talk"? 

I find that for myself, I have become a woman confident yet insecure...though that sounds weird and contradictive its my reality. With everyone else, I am this strong, beautiful, independent woman and mother...with him, I breakdown and find myself feeling miniscule because of history. I find myself questioning where I have no place questioning. Its stupid, I tell ya! I am so not that person!

So, when I think about my exes and what roles they play in my life, I think in many different tangents. There are some I let go, there are some whom I remain friends with...its my choice! Not a new s/o, not an old s/o, not my kids....just me!