Ask Dr. Mona

It’s incredibly tough to witness your child act this way toward a sibling, especially when it feels so out of character in other settings. You’re not doing something wrong, and you’re not alone in navigating this. Sibling aggression can show up in really intense ways, particularly when a toddler or preschooler is trying to process big emotions, a changing family dynamic, or even just the day-to-day frustrations of sharing attention and space.

At 3.5, your son is still learning how to regulate impulses, and his sister may feel like a “safe” target because she’s always there, and the relationship is close and emotionally charged. That doesn’t mean we excuse it, but it does give us a place to start.

Here’s something to try:

• Set clear, consistent limits: Calmly but firmly interrupt the behavior with something like, “I won’t let you hurt your sister. That’s not safe.” Then, physically separate them if needed.

• Supervise closely during high-risk situations and intervene before it escalates.

• Shift to what you do want him to do: “If you’re mad, you can stomp your feet or come tell me. But I won’t let you push.”

• Model repair: After things cool down, help him check in with his sister: “She’s crying because that hurt. Let’s help her feel safe again. Can we bring her that toy?”

I also really like pointing out the positive moments. If he lets her go first or waits his turn, you might say, “Wow! I love how you waited for her to climb the stairs. You didn’t push! That was so kind!” It reinforces the behavior you want to see more of and reminds him that he gets your attention for the good stuff, too.

Sibling dynamics can be messy, emotional, and always changing (even in the minute!). With time, consistency, and connection, kids can grow into those relationships…even if it’s not smooth every day.

This PedsDocTalk podcast episode might also be helpful. It covers sibling jealousy and how to normalize temperament and foster change when a toddler shows aggression.

This is a super common situation, especially for older toddlers who are fully capable but resistant. Around age 4, it’s less about “readiness” and more about control. Many kids who pee on the potty with no issues still hold out on poop because the experience feels different, or they’re used to the comfort of a pull-up. The added pressure of a VPK deadline can make everyone feel tense, but we want to avoid power struggles that end up prolonging the process.

Sometimes it helps to think about why he might be holding back. At almost 4, you might be able to figure that out. Maybe it’s fear, maybe it’s a control thing, or just habit at this point. Even if you're not sure, here are a few options to try:

• Normalize poop and make the bathroom a low-pressure space: Read books about pooping, use humor (make it lighthearted), and let your child explore the bathroom with a sense of ease. The more familiar and relaxed they feel, the less scary the process becomes.

• If your child responds to rewards, this might be the time to lean in: Sometimes it’s just a little thing, like letting them use sprinkles in the toilet after trying, or earning a sticker toward a bigger reward. This can add just the right spark of motivation. Keep it fun and short-term, and phase it out as the habit builds.

• Offer some control: Give him a sense of control by involving him in the process. You can say, “You’re great at going potty. How can I help you feel ready for poop, too?” Or offer choices: “Do you want to try after breakfast or before your bath?” Even deciding what book to read or what color sprinkles to use can make him feel like he’s in charge, without giving up the boundary.

And when you do see progress, even just sitting on the potty or talking about poop, celebrate it: “You sat down to try, even though it felt hard. That’s a big step!” This phase can feel stressful (especially with school), but it often resolves quickly once the pressure is off and kids feel more in control of the process.

If you’re thinking about potty training or just starting, check out the PedsDocTalk No-Pressure Potty Training Course for a step-by-step, no-stress method to get your child using the toilet!

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Dr. Mona will answer these questions in a future Sunday Morning Q&A email. Chances are if you have a parenting concern or question, another parent can relate. So let's figure this out together!