Smartmom and her sister Diaper Diva love talking to each other about their kids. Whenever they get together for coffee on Seventh Avenue, at ConnMuffCo or Sweet Melissa, it’s a non-stop debriefing session about the latest, breaking news on Teen Spirit, the Oh So Feisty One and Ducky.

Without a doubt, it’s what they talk about more than anything else.

More than their husbands. And they talk about them plenty.

More than their parents. And they talk about them plenty.

More than their friends. And they talk about them plenty.

More than their careers. And they talk about that plenty.

So what do they talk about when they talk about their kids? In a word: everything. No detail is too small, no subject is too big. They both seem to be intensely interested in each other’s children. And that’s a good thing because otherwise they’d be bored to death.

Over skim lattes, Diaper Diva fills in Smartmom on the minutiae of 5-year-old Ducky’s day. What time she woke up, how she jumped into her parent’s bed for a big snuggle, the cereal she ate for breakfast, what she’ll have for lunch.

Diaper Diva tells Smartmom how Ducky insisted on wearing her red tutu to school and her multi-colored Mary Jane sneakers; that “Alvin and the Chipmunks: The Squeakquel” is her current favorite video, that “The Magic Schoolbus” is her favorite book series, and Magenta is still her most cherished stuffed animal.

Lately, they’ve been talking about how to get Ducky to stop sucking her thumb. Smartmom was a thumb-sucker until she was 10-years-old, so she knows how hard it is to quit. When she was in fifth grade, her mother offered her $10 to stop sucking and that’s when she finally “joined the unhooked generation.”

“Ducky says, ‘My thumb is so delicious,’ ” DD tells Smartmom.

“I remember how good it tasted,” Smartmom says sticking her thumb in her mouth for old time’s sake.

“But I want her to stop,” Diaper Diva tells Smartmom.

“Don’t worry, she’ll stop eventually. I did,” says Smartmom pulling her thumb out of her mouth.

In an informal way, they both get equal kid-talk time. When Diaper Diva finishes with Ducky’s morning, Smartmom starts on OSFO.

“Her alarm went off at 5:30 am, but she didn’t wake up until 7. And then it was rush, rush, rush to get her hair, makeup and outfit together in time to leave by 8,” Smartmom tells Diaper Diva before launching into Teen Spirit’s late-night shenanigans.

“Teen Spirit came in late and stayed up even later watching ‘Breaking Bad’ on Hulu,” she tells her.

DD knows the size of Teen Spirit’s skinny jeans and the lyrics to many of his songs. She knows about his propensity for sleeping late into the day, his college applications and his road trip to Austin, Texas.

Diaper Diva knows the names and faces of OSFO’s friends and all the latest gossip. She knows the brand of OSFO’s favorite eyeliner, her shoe size and that she still likes playing with her American Girl dolls.

Needless to say, she knows about other things, too. Smartmom can brag a blue streak and not worry about sounding cocky around her sister. She told her in excruciating detail about the performance of Teen Spirit’s band Bad Teeth at Vox Pop last October. “He was really great,” she told Diaper Diva. “And I’m not saying that because I’m his mother. “He’s REALLY talented.”

Diaper Diva believed her.

And it’s not just the good stuff that Smartmom tells her sister. She also shares her worries, her insecurities, her deep dark fears. She can say things she would never say to anyone else for fear of judgment or even Child Protective Services. Diaper Diva knows all the really dumb things Smartmom has done and all the near misses (like the time Teen Spirit nearly drowned in the bathtub).

She knows things Smartmom would NEVER EVER write about in her column so just forget it.

Likewise, Smartmom knows about all the times Diaper Diva loses her temper or spends too much money on Ducky or yells too loud or lets her get away with murder. She knows her proudest parenting moments and the stuff she’s embarrassed about.

The sisters like to think that their conversations are judgement-free. But the truth is, they do occasionally act mean and judgemental. They are sisters after all. Smartmom really had a fit when Diaper Diva told her she should have NEVER let OSFO dye her hair blue.

“But she wanted blue,” Smartmom said.

“You don’t have to do everything that she wants,” Diaper Diva spit out.

Ouch.

Oh yeah? Well, Smartmom hates it when Ducky gets time-outs when she’s over.

“I hate to hear her cry in her room,” Smartmom told DD.

Diaper Diva thinks Smartmom should build new closets in Teen Spirit and OSFO’s rooms.

“They have nowhere to put their clothing. It’s such a mess,” she told Smartmom.

It can get ugly — and someone sometimes storms off. It’s pretty embarrassing to be left sitting alone at Sweet Melissa just as the waiter brings DD’s oatmeal.

“Can you wrap that up?” Smartmom tells the waiter with studied nonchalance. “She had to go.”

The sisters usually make up within an hour or so because they know it’s futile to stay mad at each other for too long. Besides, there’s always something new to talk about — and who else are they going to tell?