It can be hard enough to maintain a good relationship with your children if there's just a limited amount of time you can spend with them. It never feels like enough, and you worry that there might be a distance growing between you.
That feeling can worsen if your ex gets a serious, long-term partner. The natural feeling is that the new man in her life might end up closer to your children than you are.
How do you cope with the emotions and fear - because that's exactly what it is - that your children might end up calling another man dad? When your first learn that your former partner has someone serious it's at its worst, because you really don't know what the future might hold.
A lot depends on the bond you have with your children. If it's strong and secure you really have no need to worry. In their minds you will always be your father, even if someone else sees a lot more of them than you. Of course, it can be hard to remember and hold on to that, and the only thing that can make you feel better is time.
The problem can be if your relationship with your children is tenuous. The trick is not to feel it's a competition between you and your ex's new man. Remember, he needs to get to know the children and form his own relationship with them, which will take time. Ultimately, however much he's around, there's no way he can replace you. Simply be yourself with the kids and try to improve your own relationship with them.
What You Can Do
It's never an easy situation, and even if you're very secure with your children, you're bound to wonder from time to time, especially if the kids take to their mother's new man (and realistically, you should hope that they do, since it truly makes life easier for everyone).
Don't shy away from asking about things they do with him - although, in most cases, children tend to be garrulous, so they'll probably tell you anyway. Try not to show any jealousy, even if it's inside. Your kids don't need to know that there's a turmoil inside your head and heart. Try not to feel to threatened, since, in all likelihood, there's no reason.
Spend as much time as you can with your kids, and take advantage of all the time you're legally allowed. Do things they enjoy, and make sure you take part!
If you don't have a good relationship with your ex, things can be a problem. All you can hope is that she doesn't try and turn the kids against you, and tries to put her new man into your place.
In that case, all you can do is be yourself and be loving with your children. Fighting fire with fire and saying bad things about your ex and her new partner is very counter-productive. It simply confuses the children and leaves them feeling very insecure. Enjoy your time with them and simply be you.