Thank you very much SH -
My Ex W has having what she define a "stable" relation with this person, that is the same she left me for a year ago. I don't know and never met this person - and until this episode there was no reason to - but I don't know what she is saying to him about me and my relation with my kids - I don't know if he thinks my kids don't have a present father that care about them, or if he feels he needs to "cover" a void. I need him to know that there are things, like going to the game, that "I" want to do with my kids, because this are memories I care they build with me, and not with him. I want him to know that when he is with my kids he is responsible not only toward my ex W but also toward me, I am not a ghost. My ex W doesn't understand my concerns and thinks I am neurotic - and probably other people think the same.
Yes I am also jealous, and afraid my kids my end up loving this person more then they love me - I know this is not reasonable a feeling, and I try to fight it.
In this year I didn't date anyone, I have been busy rebuilding my professional life, besides my spirit - I have been wishing all along my ex W reconsidered her decisions, but not much luck there, our relation had good friendly moments, some few moments where there was an hint she was reconsidering, and few horrible fights like the one we are having now, where I am digging myself a hole because she is immediately arguing I am over controlling, but I don't think I am, and I have never been - she always did what she wanted without ever consulting with me, while
I have always involved her.
I tried to be the inspirational super Rop. Sometime I succeed many time I fail, I am human, I have miseries and jealousies, but I don't think I am worse or better than anyone on this planet. Yes "they" are watching me - and I am watching "them". My kids are very small and vulnerable, I don't want that they have the wrong message about what a father is, specially that no one can, just because has a relation with their mother, claim any rights about them. I raised my kids, I saw them born, they are my life, this guy is nobody, and a perfect stranger to me, and I want him to back off from my kids - is that weird?
I don't know if the law protects me and my kids, in anyway about this - I know it should - I don't want to do anything stupid or illegal this is why I am so eagerly asking you guys if you have experience on this.

Here are my answers to your questions:
QUESTIONS:
1. Is the problem THIS OM, or any OM?
//The problem is that I don't know this person at all and I don't know his motivations. That when is about my kids is not just my ex W has a saying about my kids but also me - is not me OR her, but me AND her. I definitely would have a problem with EVERY OM around my kids by themselves - I am ok if my Ex W is there with them.

2. Does something about this OM in particular disturb you?
Well - he went with a married woman with two small kids, we definitely don't share the same moral values - but my main concern is that I don't know this person at all. Just because my Ex likes him doesn't mean is a person I want around my kids.

3. Is XW developing a pattern with new FotMs?
No - she has been with this guy since.

4. Are you hoping to reconcile with XW?
I hope I could rebuild my family together, I am still very upset with my ex, and it wouldn't be an easy task - but for sure OM is a big obstacle.

Thank you very much