We have almost 500 dads in our Slack group. And this question comes up more than almost anything else.

When should we have another one? Larger age gap or smaller? Anyone have pros and cons for a big or small gap?

It’s one of those questions that feels like it should have a clean answer. A formula. A right move. It doesn’t. But there’s a lot of useful thinking out there from dads who’ve lived both sides of it. And there’s one bigger truth that tends to override all the planning anyway.

More on that in a minute.

What the Research Actually Says

If you go looking for scientific guidance on ideal sibling spacing, you’ll find a lot of hedging.

The most commonly cited sweet spot in parenting research is somewhere between two and three years. The reasoning makes practical sense. Mom’s body has had meaningful recovery time. The older child is out of diapers and old enough to understand what’s happening. The logistics are manageable.

But the research also consistently shows that the effects of age spacing on sibling closeness and child development are heavily influenced by other factors: personality, parenting style, family dynamics, and frankly, how the parents handle the chaos.

There’s no gap that guarantees close siblings. There’s no gap that guarantees difficult ones.

What the data is clearer on is the stress curve. Very close gaps, under 18 months, are significantly harder on the parents in the short term. The physical and emotional demands of two babies essentially at the same time are real. On the other end, very large gaps, five years or more, tend to produce more of a separate-childhoods dynamic where the kids have less overlap in life stages and sometimes less natural closeness.

Everything in between exists on a spectrum. And the people living it are the best source of actual data.

What Our Guys Said

The Dad Day community had thoughts.

  • Jon, who has a 2.5-year gap, put the logistics case well: “Larger gaps are hard because when you finish a milestone the other is entering it. Diapers, daycare, etc. Two years is nice because they can still be in a similar friend group.”

That overlap point is real. With a closer gap, you’re buying diapers for two kids at once, yes. But you’re also finishing that phase faster as a household. With a larger gap you get a breather, then you restart from scratch. Depending on your tolerance for restart, that’s either a relief or a grind.

  • Eric also in the 2.5-year camp, described something that’s hard to put a number on: “They’re so bonded and literally follow one another’s lead in both directions all the time. It’s pretty special to see their closeness continue to grow.” He also noted a practical win he didn’t expect: “Our second was way faster to get out of diapers because he was following the leader.”
  • Richard O. offered the longer-gap perspective from lived experience: “With my 4.5-year gap to my middle brother and another 4.5 to the older, we didn’t bond much as kids. We get along fine, but we couldn’t share a lot of interests at the same time and definitely couldn’t share friend groups.”
  • Daniel had the line of the whole conversation. With 2.5-year-apart kids himself, he described his own family of origin, where brothers 13 months apart grew up extremely close, and then there’s Daniel, arriving 6 years after the last sibling. “I was kind of on my own. But it took my parents 5 tries to finally get it right.” 😏

The Thing You Can’t Plan For

Here’s where we want to be honest about something.

All of this assumes the universe cooperates with your timeline.

Our boys are three years apart. We now have a five-month-old girl. And part of us wishes we would have just gone for all three a lot sooner. But number three didn’t come easy. There were things we couldn’t control and didn’t plan for. And so we feel genuinely, deeply blessed to have three healthy kids. Full stop.

That’s the part of this conversation that doesn’t get said enough.

You can read every article, poll every parent in your life, make a spreadsheet if that’s your thing. And then biology, or timing, or circumstance, or something completely outside your control enters the picture and changes the plan.

The couples who planned an 18-month gap sometimes end up with four years. The couples who wanted to wait ended up surprised sooner. The ones who thought they were done ended up with a beautiful third who came when they least expected it.

The gap between your kids is something you can have intentions about. It’s not something you can always control.

So What Do You Actually Do With All of This?

A few things that seem genuinely useful.

Think about the phase overlap honestly. Closer gaps mean more concurrent chaos. Double strollers, double diapers, two kids who both need you physically at the same time. It’s hard and then it eases. Wider gaps mean less concurrent chaos but a longer total runway of the intensive early years. Neither is objectively better. One might fit your life better than the other.

Think about sibling closeness differently. Closeness between siblings isn’t primarily a product of age gap. It’s a product of how the family operates. Kids who are encouraged to play together, who spend time together, who are raised in an environment that values the sibling relationship, tend to be close regardless of the gap. You have more influence here than the birth spacing does.

Don’t optimize too hard. The families who seem to navigate this best are the ones who made a reasonable decision, went for it, and then adapted to whatever actually happened. Over-optimizing the gap is a way of trying to control something that is, at best, partially controllable.

Give yourself some grace. Whatever gap your kids end up with, whether it was planned or not, there are people living that exact situation and doing great. The gap doesn’t determine the outcome. You do.

We’ll Leave You With This

There isn’t one right answer.

Two to three years seems to be the most commonly recommended range and there are real practical reasons for that. But people with 18-month gaps have beautiful sibling relationships. People with five-year gaps have beautiful sibling relationships. And some people with two-year gaps still have kids who aren’t particularly close.

Have the conversation with your partner. Think about your bandwidth honestly. Make a plan if it helps you feel grounded.

And then hold that plan loosely, because the universe tends to have opinions.