Q. The guy I have been dating for a year just told me that his ex and their daughter are moving back in with him. Evidently, his daughter is very sick, and his ex can’t take care of her by herself, so he suggested they move back in with him.

We do not live together, but we were talking about it after the first of the year. Now those plans are on hold. Although he has assured me this is just an arrangement of convenience, I’m not comfortable with the whole thing. What’s good ex-etiquette?

A. Good ex-etiquette starts with “Putting the children first,” which it sounds like your boyfriend is trying to do, but — and this is an all caps BUT — the arrangement you describe would make just about anyone in your position uncomfortable. You have quite the predicament.

Co-parenting relationships are often unconventional, and this can be difficult for new partners. The degree of intimacy — and I’m not talking sexual intimacy, but merely the need to talk to someone as often as necessary when you share a child — can be unnerving for new people in your life.

It’s understandable if you’re saying, “Hey, wait a minute.” So, let’s examine some background and see if there is cause for alarm.

The key question is: How forthcoming has your boyfriend been? Because how comfortable you feel and how you envision your future with this man is dependent on how honest he has been with you.

If he has integrated you into his life with his daughter and introduced you to her mother to set the stage to form a cordial relationship, that would have been a positive step. However, if he has kept you separate, you don’t know his daughter and have never met her mother. And now she’s moving back in? That’s a red flag.

Not being forthcoming would indicate to me that he’s closer to his daughter’s mother than he has led you to believe. (Ex-etiquette for Parents rule No. 8 is “Be honest and straightforward.”)

Most new partners do not anticipate how disruptive dating a parent can be. They approach any new relationship as a first-time partnership and that is simply not the case when dating a parent. Parents must constantly juggle their attachment to a new partner with their responsibility to their children.

This reality can make new partners feel second best. Don’t do that to yourself. The relationships are completely separate and should not be compared.

Although a situation as you describe can be quite disconcerting, it’s the type of unpredictability you may face when dating a parent. A sick child takes precedence, and co-parents must learn to put their heads together to figure out solutions, particularly when facing the unexpected. A better approach might have been for Dad to have talked to you about it as the decision was being made. This would not necessarily be to weigh in because, ultimately, a sick child’s destiny is the parents’ decision, but instead to keep you in the loop. That way you could observe and feel as if you were part of the process rather than have it sprung on you with no say about how your life might change.

That said, depending on how sick this child is, you may have to put moving in together on hold for now. Or, depending on how involved you and the parents want you to be in the child’s recovery, you could be part of the solution, as well. Try not to take this personally. Have that discussion. It doesn’t have to be either/or. Look for solutions in the name of the child. That’s good ex-etiquette.

Blackstone is founder of Bonus Families, www.bonusfamilies.com, and may be contacted at dr.jann@exetiquette.com.