Sienna and Saskia Sibley are sisters who both work in the theatre industry, with Sienna having played Jane Banks on tour in Mary Poppins, before Saskia took over the role last year. Sienna most recently finished her run as Georgina Trimble in Oliver! in London’s West End, with her other roles including playing Lily Potter Jr in Harry Potter and the Cursed Child at the Palace Theatre, Young Elsa in FROZEN the Musical, and she was in the casts of Roald Dahl’s The Witches at the National Theatre and Les Misérables in London as Young Éponine and Little Cosette. In 2025, Saskia played Little Cosette on the Asian leg of Les Misérables: The Arena Spectacular, which marked her first time performing in a musical abroad, and she returned to the show earlier this year at 3Arena in Dublin and the Royal Albert Hall in London, having originally performed as both Young Éponine and Little Cosette in London’s West End. Talking with us, Sienna and Saskia told us about what it’s like being in the acting industry alongside your sibling, their times in Mary Poppins and Les Misérables, Saskia’s experience performing abroad with Les Misérables: The Arena Spectacular and Sienna’s recent run as Georgina Trimble in Oliver!.

As two sisters working in the acting industry together, what is it like having both of you audition for roles and be able to go to each other for advice?

We think that it is very useful for us both doing auditions because if one of us has previously auditioned for the show or played the role before, the advice we can give each other is very accurate, and we can talk about our past experiences.

What do you each enjoy most about being an actor, and is there anything you find most challenging?

The things we enjoy most about being an actor is meeting new cast members and exploring different styles of theatre. Something that we find most challenging is using different accents. For example, in Mary Poppins, we both had to perfect an RP accent and in FROZEN, the role of Young Elsa that Sienna played has an American accent.

You have both been part of major musicals in the West End and on tour, how does it feel watching each other on stage?

It is very special watching each other on stage, as we know all the hard work that has happened to get there, from the auditions, the rehearsals and then opening and seeing each other so happy on stage. It’s a very proud moment. We have both been cast in a couple of the same shows at different times, so it’s always fun seeing how we play it differently and bring ourselves to the part.

What are some of your favourite highlights from playing Jane Banks on the UK Tour of Mary Poppins, which Sienna played first before Saskia took over the role at the end of last year?

One of the highlights of Mary Poppins was getting to know the actor who played our on-stage brother, Michael. Sienna’s brother joined the show when she did, so he was with her from the start, meaning they had loads of time to connect with each other and build up their relationship ahead of opening. Saskia’s brother was already in the show, therefore was paired with another girl, so they had less time to connect, but they ended up having a blast.

This is our highlight for us because we became the best of friends with our brothers and can’t imagine doing the show with anyone else.

What was Jane Banks like to play, and how was it finding out you would each be playing the role?

Playing the role of Jane Banks is definitely a tricky one. She is in the show non-stop and has minimal breaks, except for the interval. Overall, it was one of our favourite jobs that we’ve done in our entire lives.

Sienna was very excited when she found out, as she had made the decision to not stay at Harry Potter for another contract so she could try for another musical theatre job before she got too tall, and this was a dream role.

Saskia was over the moon when she found out she was going to get the role of Jane and would be taking over from her big sister Sienna. In the programme for Milton Keynes, we were both in the programme side by side, as that was the venue that Sienna finished her run and Saskia started hers, so that was very special.

Sienna, you have recently finished your run as Georgina Trimble in Oliver! at the Gielgud Theatre in the West End, what was the musical like to be part of?

I loved my role as Georgina Trimble because of how strong she was, and it’s a brilliant show to be part of. The dancing was so fun but never failed to get me out of breath. As for the people there, my whole team was full of boys, which at first I was worried about, but as I got to know them all, my doubts went away. They were all so lovely, and I have made forever friends.

Sienna, how was it performing in Harry Potter and the Cursed Child at the Palace Theatre as Lily Potter Jr, and how different did you find it to your other projects?

Performing in Harry Potter and the Cursed Child wasn’t something I normally did, as it was a play which only involved acting, but I loved the new experience and the challenge, and I miss it with all of my heart.

Sienna, what was it like joining the Disney production FROZEN the Musical as Young Elsa, and how was it getting into character?

Playing a Disney princess is something every child dreams of once in their life, and I’ll be forever grateful for getting the opportunity to play Young Elsa in FROZEN. One challenge I did have to face was the American accent. For me, it was hard to sound natural talking in a different way to how I usually do. However, the creatives were so helpful and guided me through it.

FROZEN, to me, is my favourite job I’ve ever done, not only because of the role but also because of all the wonderful people that I shared the role with and played alongside. I couldn’t have asked for a better set of creatives, chaperones, cast and crew members.

Sienna, can you tell us about your time in the casts of Roald Dahl’s The Witches at the National Theatre and Les Misérables in the West End as Young Éponine and Little Cosette?

My experience in The Witches was one I’ll never forget because I was the youngest out of 30 children, and we were rehearsing for a new musical, meaning loads of scenes were cut, lines were added and the tech rehearsals were so long. However, the roles were very fun, as each character I played had a different backstory and style to them. I would happily go back and perform the show again.

My time on Les Misérables was exciting at the time because it was my first ever job. I remember stepping on stage for the very first time in front of thousands of people and doing the thing I loved. Even though it was a small role, I was very proud of myself because I was only seven.

Saskia, how did you find the experience performing on the Asian leg of Les Misérables: The Arena Spectacular last year as Little Cosette, and how was it working on a musical abroad for the first time?

I loved playing Cosette on the Arena Tour of Les Misérables. It was so exciting but also a bit nerve-racking because I had never been away from my family for that long. I was used to performing in theatres not arenas, so that was a big change for me, but the atmosphere was amazing and I had a brilliant time.

Saskia, what was it like returning to the show earlier this year and performing at 3Arena in Dublin and the Royal Albert Hall in London?

When I found out that I would be playing the role of Cosette again in Dublin and at the Royal Albert Hall, I was ecstatic because they are such big and iconic venues. I was also shell-shocked by the famous people I was playing alongside, such as Marina Prior, Matt Lucas, Samantha Barks and Alfie Boe.

Saskia, you’ve previously played both Young Éponine and Little Cosette in Les Misérables in the West End, do you have any stand-out memories from the West End run that you can share?

A stand-out memory I have from Les Misérables in the West End was our last show before Christmas. We got to have Domino’s Pizza in the dressing room and play fun games. We did a Secret Santa, and one of the chaperones brought a mini mic in and we got to do karaoke. The song I sang was Popular from Wicked, and I sang it with my Éponine.

How did you each get into acting and did you both always know you wanted to perform on stage?

Our mum used to be a professional ballerina, and she put us into dance classes at a young age at our school KA Arts. It was here that we met our agent – EJC Management – who scouted us whilst watching us in our dance class. She gave us loads of opportunities to audition for things such as adverts, TV shows and films, until she put Sienna forward for Les Mis at the age of seven, and she got the job. After that, we were doing loads more self-tapes for musicals, and that is what led us into loving theatre.

What are each of your favourite theatre shows to watch, and are there any you would like to see that you haven’t done so as yet?

Our personal favourite theatre shows to watch are Annie, SIX and Wicked. Some shows we would like to watch that we haven’t yet are Hamilton, Little Shop of Horrors and Billy Elliot when it opens.

How do you like to spend your time away from acting?

We both like to spend quality time with friends and family. We love going to the shopping centre, watching Netflix, going out to eat and having phone calls with our friends.

How do you typically prepare for new roles and auditions?

We like to look at the material that is given and, if we have to choose a song for our audition, we pick out of a selection that we have in mind and keep practising them until the day of the audition. We also like to do a little bit of research on our role to get a clearer understanding of what to do in the audition room.

Do either of you have any projects coming up that you can tell us about, and what are you hoping the rest of the year brings you?

Saskia has a few auditions coming up that she’s busy practising for and would love to book another show. Sadly, Sienna has limited opportunities in musicals now due to her height, as most shows have a maximum height of 4’10”, so she is going to focus on her training and more screen work. But who knows what is around the corner!