Q. My ex is having a small holiday get-together a couple of weeks before Christmas, and all our kids and their significant others are going. Although we usually both go to all the family festivities, I haven't been invited to this one. Our youngest daughter says it was just an oversight and I should go, but I'm not so sure. I don't think my ex's new girlfriend wants me around. What's good ex-etiquette?

A. We could speculate about all sorts of reasons why you weren't invited, but the bottom line is you weren't — and that's a red flag. The standard rule of party etiquette, not necessarily ex-etiquette, suggests you don't go to parties unless you are invited by the host. Of course, there are the sorts of parties where there's a "come one, come all" open invitation, but this doesn't sound like that.

There's a reason why you weren't invited to this one — and, if you take this at face value, it looks like your children's father wants to start doing some things separately. That's his prerogative, and perfectly good ex-etiquette.

If the girlfriend prompted this new attitude, that's Dad's problem. It could be that he is being bullied or he could agree that you shouldn't be around. Either way, it's his decision, and if you're following good ex-etiquette, it's your responsibility to respect the other parent's turf.

It's also good ex-etiquette to set clear boundaries. If Dad wants you to attend, it's his responsibility to ask you, and if he wants his girlfriend to back off, he's the one who should be making that clear.

From my personal Christmas diary, for years my husband and I and the combined kids spent Christmas Eve with family friends. Because we alternated Christmas Eve and Christmas Day, sometimes my bonus kids were with us, and sometimes they were not. One year we walked in to see their mom sitting at our friends' kitchen table. I quietly joked to the host, "Uh, what's with inviting my husband's ex-wife?" He said, "We did that for you."

I had been talking about how well we were all getting along and how hard it was on the kids going back and forth around the holidays. Their solution was to invite everyone. After a deep breath and really looking at the situation, I was glad they did. The kids were delighted. The next day we had our Christmas morning, then off to their mother's home they went. No fighting. No hurt feelings.

Here's a good ex-etiquette rule of thumb for holidays and other family get-togethers: If the get-together can easily be repeated, such as a dinner party, for example, then celebrating together may be overkill. If it's a special occasion such as a graduation or possibly a holiday where a tradition is in place and the children will be affected, it would be understandable if both parents attend.

The choice is always personal. Good ex-etiquette comes into play when parents make a decision not on how they feel, but based on the best interests of their kids.

Jann Blackstone is the founder of Bonus Families, bonusfamilies.com.