Hey now, hey now. Hilary and Haylie Duff's relationship is what dreams are made of.

Hilary was our best friend growing up, and she's still our best friend today. We grew up with her, she gave us the soundtrack to our childhood, and she became even stronger when she was with her twin-like sister, Haylie.

Before she was a teen idol and an inspirational mother, she was a sister. Throughout Hilary's successful career, she's always had the support of her older sister. Now they're mothers together, raising their kids to be just as close as they are. They even spent quarantine together.

Here's what our favorite sister's relationship is really like.

They Collaborated A Couple Of Times

Hilary has always looked up to Haylie. When she saw her sister rehearsing in 2001, Hilary knew she wanted to become a singer just like her. So she signed a music contract with Radio Disney.

On her 2003 album, Metamorphosis, Hilary and Haylie had their first collaboration with the song, "Inner Strength." Hilary said that writing with Haylie was a "specific comfort place" during a time in her life when things had been changing "so fast and so quickly."

Related: Hilary Duff Has Changed A Lot Since Lizzie McGuire

When Hilary's days as Lizzie Guire ended in 2004, it left the door open for her to explore what she wanted to do next. Right out of the gate she gave us a film with Chad Michael Murray, A Cinderella Story, and her second collaboration with her sister.

At the end of the film, the sisters sing a cover of the Go-Gos song, "Our Lips Are Sealed," and they made the music video too. It was all we needed.

Then the sisters went on tour together, where they bonded even more, and sometimes saw strange things happen on stage. "This little girl was in the audience and Haylie touched her hand. She had pulled hair out of her own head, a whole huge (lock) of her own hair, and handed it to Haylie," Hilary told People.

Shortly after they starred in the comedy, Material Girls in 2006. They ended up getting a shared Razzie Award for Worst Actress, but we still loved the sisters working together. They also collaborated on a cover of Madonna's song "Material Girl" for the film's soundtrack.

Related: Here's How COVID-Exposed Hilary Duff Is Spending Her Self Isolation

"We’ve kind of been waiting for the right time to do something together," Haylie told People about their film together. "Everyone kind of thought it was the natural thing for us to do. So, to get to finally do it is really cool. We’re excited, especially because we get to keep our wardrobe."

Around this time, Hilary revealed that her sister gave her inner strength when she was just getting famous. "She’s really good at analyzing people and giving me advice about that. I kind of got hit really hard when people started knowing who I was – people talking bad about me, and this stuff coming out about our family. And she was like, 'Hilary, don’t let it get to you. You know, you’ve seen it a million times with other people.' She just always made me feel really good about it."

They were never competitive with each other either. "When we were auditioning and stuff, we’d be like, 'If I don’t get it, I hope you get it! Or if you don’t get it, I hope I get it!' You know? It was never ever like (competition)," Hilary said.

Through both their careers, they supported each other and never lost their closeness.

They're Neighbors

When Hilary got engaged to Matthew Koma in 2019, Haylie revealed that their wedding would be traditional but she wasn't going to be helping her little sis plan because "we're very different."

But in the end, Haylie was a part of the special day and confirmed to Us Weekly that her two daughters, Ryan, who was four at the time, and Lulu, who was 19 months, would be part of the wedding. She said Hilary looked absolutely beautiful on the day.

Haylie went on to say that her children were really close to Hilary's two children, Luca, 7, and Banks, 15 months. Not only are they cousins, but they're also neighbors.

"They’re so close in age and we live down the street from each other, so they bond the way normal cousins bond," Haylie said. Lulu and Banks are only four months apart from each other.

Despite having kids similar in age, the sisters don't try to give the other advice on parenting. "We try to listen to each other and be there for each other," Haylie told People. "Everyone has so much advice all the time, so we really just try to support each other whenever we feel like venting or talking something out."

Related: 20 Photos Showing Hilary Duff's Transformation Through The Years

"It’s really special; it’s nice for them to be able to grow up together," she continued. "We had a small family growing up, so we’re excited that we’ve got four cousins close in age that can play together."

During quarantine, the two sisters would wave at each other from over their gates. Haylie told Hollywood Life that she and Hilary's families were dealing with isolation pretty well.

"We have different people that we see, so we’ve been trying to be very careful about not co-mingling, just for the sake of people that work in her home or people who work in my home," Haylie said. "So, we see each other from afar and wave outside at the pool."

One thing that'll never change is the sister's tradition of coming together during the holidays. Hilary is very particular about having turkey and Haylie, who's known for her great cooking skills, will make it for her every year. That's great but when will they go back on tour together? We need to know.

Next: Very Pregnant Hilary Duff Realizes Fans Won’t Be Buying Her Rompers