My Stepdaughter’s Dog Just Moved In. He’s Tearing the Family Apart.

Care and Feeding is Slate’s parenting advice column. Have a question for Care and Feeding? Submit it here .

My husband, “Jared,” and I each brought a child into the relationship. I have a 13-year-old daughter, “Melanie,” and Jared has a 9-year-old daughter, “Chrissy.” Now we’re at an impasse over Chrissy’s chihuahua, “Nacho.”

Nacho lives with Chrissy’s mom. Or did. Recently my stepdaughter’s mom got priced out of her rental, and the place she moved to doesn’t allow dogs. I reluctantly agreed to let Nacho move in with us so Chrissy wouldn’t lose her dog. The trouble is that Nacho hates Melanie. He barks at her constantly and from day one attacked her legs. She now has to wear soccer shin guards around the house when Nacho isn’t contained. I’ve tried to be patient and we have tried to get Nacho trained, but nothing works.

Now Melanie’s dad is saying either the dog goes or Melanie comes to live with him full-time. Since Nacho moved in, Melanie has been spending most of her time in her room. I don’t think she should have to choose between being a prisoner in her own home or leaving all together. My husband says it would be “cruel” to make Chrissy give up her dog and it’s just a matter of finding the right training program for him. Jared even has Chrissy working on me and Melanie pleading for Nacho to stay. What can be done?

The way you handle this must make both girls feel loved and welcome in your home. The only scenario under which Nacho can reasonably stay is if he is restricted from Melanie’s presence at all times, using gates, crates and outdoor time to keep him separate. If you can’t ensure that he won’t have access to her, then he should have to go. A training program may be helpful and that’s a step that needs to be taken immediately. Assure Melanie and her father that Nacho will not be in the same space as her, that you are sorry for what happened previously and that if it happens again, he’ll be out with no discussion. Let Chrissy know that you want to make things work for her and her pup, but that you can’t allow Melanie to be unsafe or uncomfortable in her own home. Rehoming Nacho will likely devastate Chrissy, but it’s a step you must be prepared to take if you can’t protect your daughter from him.

I have two children, my daughter “Pam” and a son “Eric,” age 12 and 10 respectively. Until recently, my husband and I were friends with our neighbors “Adam” and “Belinda,” who also have kids around the same age. About a week ago, we were over at their place, and as usual, the adults sat around and chatted in their library while the kids played. Pam was sitting with the adults and plucked a book off the shelf to start reading. Adam noticed almost immediately, said that that particular book wasn’t for kids, took it away from Pam, and offered her a different book instead. I was curious about the sudden and vehement reaction.