Aly and AJ Michalka have become "closer as sisters" in recent years

She told UsWeekly: "Aly found out she was pregnant with him the night we played the Greek [Theatre in L.A.]

"There's this throughline that he's been with our band for a while and being an aunt is truly the best. I always joke, it's literally the best role I've ever booked. It's so fun.

"[He's] brought us not only closer as sisters, but also brought us to a state of embracing this childlike wonder that maybe we lost a few years ago that we had when we first started making music."

Meanwhile, the 'Potential Breakup Song' hitmakers have had to change their riders over the years, and AJ revealed that their must-haves these days are more to do with looking after themselves so they feel "comfortable" when showtime comes around.

She said: "We try to change our rider a little bit every tour. For the most part, it's kind of always the same. I kind of feel like we actually do need a whole new makeover on it for 2025. But in general, what I go to preshow is tea. For me, it's very important to drink Throat Coat. I'm not a huge fan of the taste, but that is one specific thing that really helps me in terms of coating my vocals and feeling comfortable about warming up and getting on stage."

However, Aly admitted that there is going to be some "some kid stuff" back on the rider as she prepares for Jack to join them on the road.

She said: "Electrolytes, that's a big one, just so that we're keeping our energy and hydration up. You sweat everything out during the show. We now have some kid stuff that's going to be on the rider, which is funny, like, peanut butter and apples and yogurt for the little dude."