Q: My co-parent and I have two kids. I recently remarried, and my wife (who has two children a few years younger than mine) insists on going to all the children's doctor and dentist appointments. That causes my co-parent to become extremely territorial and recently caused a brouhaha at the dentist's office. My wife thinks she's in the right, and it's my ex's problem. What's good ex-etiquette?

A: Your wife's out of line. Unless her children also have appointments, there's no reason she should attend your children's appointments unless she's asked to be there.

Ex Etiquette Rule No. 4 is "Bioparents make the rules, bonus parents uphold them." Bonus parents should not interfere in an already established co-parenting plan — unless, of course, he or she has children of their own in the home. Then it's a carefully orchestrated dance combining past and present rules using all the kids as the criteria for decisions.

Better that your wife works on building a cordial rapport with your co-parent so they can keep communication open and problem-solve in the best interest of the children.

When I first started my bonus family arrangement, my bonus kids' mom and I would make appointments for the kids when they were scheduled to spend time with us — and then not tell the other. Everyone was jockeying for position.

The war ended when we realized we needed each other's help. Too many kids, too many working parents going in too many directions. As a result, there were times my bonus kids' mom reached out to me to take the kids to a previously scheduled appointment — and vice versa.

Parents who no longer are regarded as a couple often feel guilty that they can't be with their kids. Add to that an overzealous bonus parent trying to take over parental duties, and that's asking for trouble.

Each parent and bonus parent should find their niche — what can they offer to the kids? Or, if co-parents must share responsibilities, like homework, look for ways to cooperate so that the kids have people to emulate. That's good ex-etiquette.

Jann Blackstone is the founder of bonusfamilies.com.