Duff's new book "My Little Brave Girl" is an homage to her kids. Cunningham particularly liked the dedication section, where Duff wrote "the cliché of not being able to love another child, as much as the first felt so real, and you completely proved me wrong."

He then asked her how it was for her to welcome a new baby in her life. Duff said that for a very long time she didn't think she was going to have another child after having the first one.... But things changed when she got pregnant with Banks:

"I always felt like I was meant to be a mother. I knew I have those instincts. And I knew that was something I wanted in my life. But you instantly start to kind of compare them, unfortunately. And you're like, 'I don't know how, but he does this thing really cute and really special. And she's probably not gonna do it like that.' Like you're instantly thinking you're not capable of having another and then she did just prove me wrong and she was really a challenging baby."

And Duff said that there are no limits to the love a mother feels for their children....No matter how many they may be:

"It just goes to show you there's just that bond there and your heart grows bigger each time and your capacity to love and create space for your children it's kind of like endless, I guess, or it feels that way. Who knows if number four came they're cut off no more love for that one."

But, for the moment, Duff clarified that they're "staying at three." And when asked about the reactions of her two other kids, Duff said that Luca is extremely sensitive and was "super excited to have another sibling" and Banks:

"She's like unphased and she's really loving. She wakes up first thing in the morning and I go to get her out of her crib and she's like, 'I'm going to pet Mae Mae'. I'm like, 'Oh, okay. You can go pet her.' I think she thinks she's like her little dog."

And Duff also shared news on the upcoming Hulu spinoff of the CBS sitcom hit, How I Met Your Father. Cagle asked her what the actress could reveal about the new series and if it'll tie in with How I Met Your Mother.

"The script was so good. I literally called and I was like, 'please, yes, please have them pick me.' The script is definitely being changed a little bit. But it does tie in and hopefully we'll have some fun guest appearances from the original cast. It does take place in New York, which is so funny, cause we are filming in LA. But, you know, there's great characters and I'm going to get to have another on set family, and another TV family."

And Duff revealed that there's going to be plenty of romance for the characters of the show:

"There's so much opportunity for like, love stories with this show because it's Sophie and then, three dudes. So it's going down that whole rabbit hole of like, well, which one was, was the one and which, who was the father. And you get to like go through all of Sophie's young experience of finding love and dating and what that's like in the modern world."

Finally, Duff reflected on the legacy of Disney Channel's Lizzie McGuire and the possibility of a modern day revival of the series.

"I think they're really trying to figure out what kind of content they want living on Disney+, and that doesn't totally align with where I see Lizzie right now and I'm like very protective of her and they're very protective of her. But the one thing for me was just the way that she could connect with what was going on in people that were watching the show. It was like they're watching themselves, and that was where they related. And so it only makes sense to me to shoot a show where she's acting like a 30 year old in a modern world."

Duff continued saying that there were lots of "creative discussions" in order to make it work. But in the end, Duff said: "I don't think it's going to be happening."

However, Duff shared what it was like for her to shoot two episodes as Lizzie McGuire once again:

"We shot two episodes and it was like lovely to relive that even for three weeks of my life because there was a point in my life where I couldn't stand Lizzie McGuire. And I was like, 'I don't want to hear that name ever again.' And now that I'm my age I love her. This is where it all began for me. And she is me and I am her. And I brought what I could to that which was very much just who I am inside. And so to tap into that again, even for a moment was really a great experience."

The possibility of seeing the original cast members was also incredibly powerful for the actress:

"And to see a lot of the original cast.... we're different humans now. And so it was just like all love. And it still is. And you can never say never in this business. I always say that sometimes I get the most random phone calls. You never know what the day is going to bring."

SiriusXM's The Jess Cagle Show airs Mondays through Fridays at 2pm ET!