My wife is confused as her ex-husband is back around.?

We married for the wrong reason, to get away from our ex's. We were most like best friends and still are. We are great lovers and enjoy each other others company. We got married in 02/07 and my ex had my kids. I didn't get to visit the kids at all at the time and it was just me and my wife, all quiet and cozy. After a series of events, 6 months later I have full custody of my two kids that at that time moved in with me and my wife in a small 2 bedroom condo. We struggled for 2 months and I finally agreed on renting a place and moved out with my kids. Meanwhile her ex got into rehab and supposidly is away from drugs and alcohol. She has two kids with him, 21 yrsand 17 yr boys of which her ex has full custody. Now she has start "dating" him along with me and she has fear in some extent towards her ex, he has a temper. Now it's to a point where she says that she is waiting for God to close one door and open the other and goes a day at the time, out with me and him.