My partner is doing more co-parenting with his ex

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I have been with my boyfriend for four years. I have two children from a prior marriage. He has two children from different relationships. I recently discovered that he has been venting to one of the mothers of his children about how our relationship is going. They had a child many years ago and were never married. She has another child who is 2. We have custody of all of our kids and live together.

All of a sudden this ex has been having visitation with her child, and has been taking the teen half-sibling (my husband's other child) on the weekends. The teen is not her child. The other day, my boyfriend brings home her 2-year-old (he is not the father of the baby), who spends the whole weekend at our house. He took it upon himself to take this child to go visit his ex's family. I am sick to my stomach. I think there is a lot more going on then being there for the kids and co-parenting. He expects me to be OK with all this. I just find it odd that she knows we have relationship issues, and now they're parenting and talking a lot. She wasn't involved in our lives very much until about three months ago. What are your thoughts?

– Sharing

I won't make guesses about your boyfriend's intentions. It's possible that he and his ex have figured out a way to be really great friends. It's also possible that there's more to it.

It's clear, though, that he isn't being considerate about boundaries and feelings in your shared home. If you're going to sign up to care for a 2-year-old for a few days, it's probably best to ask your partner first. There should be conversations about what's comfortable for you and your children.

I will say that the terms of co-parenting can change over time. Sometimes the initial rules no longer apply, and as everyone starts figuring out a good system, there's more shared time. If he and this ex are getting along and finding new ways to help each other, that's great. But these changes can't happen without major communication – with you. You should talk to your partner about how these decisions are made and what boundaries might be best for the household. Maybe consider some help from a counselor.

You can also talk to him about how this is making you feel about your romantic relationship. It's OK if he wants to confide in friends about problems, but why her? Does he understand why that might make you uncomfortable and insecure? Ask him how this can be better for both of you.

– Meredith

Readers? Is this new closeness a problem? How do you negotiate the blending of families?