We’re not ready for the end of The Big Three! (Picture: Instagram @mackenziehancsicsak)

Warning: Spoilers ahead!

This Is Us fans are already in bits over the series ending, after an emotional rollercoaster across six seasons with the Pearson family.

But now, there’s even more nostalgia added to the mix as one of the stars of the show posted some snaps of the cast together, including pictures of the actors and actresses playing The Big 3 at different ages.

The programme, which stars Mandy Moore and Milo Ventimiglia, follows the lives of three triplets, Kate, Kevin and Randall, with their parents Rebecca (Mandy) and Jack (Milo).

Flicking back and forth between their childhood (from when Randall was adopted at birth), their teenage years (after Jack died and left Rebecca to raise them as a widow), and their adult lives (with their own children and caring for Rebecca through her dementia), the show producers cast four different Kates, Kevins and Randalls, all at different ages.

Though they never appear in the same scene together, viewers have been treated to some pictures of the cast, including one of all four Kates posing together.

We’ve got our tissues ready for the final episode! (Picture: NBC)

Mackenzie Hancsicsak, who plays 14-year-old Kate, shared the sweet snaps to Instagram, writing: ‘Watching the series finale today with my @nbcthisisus family. It was amazing to see how #danfogelman closes the final chapter with the Pearson family. It was nice seeing everyone and also meeting fans of the show. Hope everyone enjoyed it! Xoxo.’

Along with the pictures of the Kates, Mackenzie shared one next to her on-screen brothers, Lonnie Chavis (as Randall) and Parker Bates (who plays Kevin).

Fans rushed to the comments to share how ‘grown up’ the actors now looked, with one writing: ‘They grow up so fast. Forever, Big 3!’

Another penned: ‘It’s been fun watching you all grow up!’ 

When those three had first started appearing on the show, they were around the ages of seven and eight, and now, are around 14.

The young Big Three started filming around the ages of seven and eight, and are now 14! (Picture: NBC Universal Media)

In another picture, the trio posed with Milo and the youngest versions of themselves, and, as if that wasn’t enough Lonnie posted on his Instagram, standing next to the younger and older versions of Randall, Caron Coleman and Niles Fitch.

He penned: ‘O-D on these Randal Pearson moments. Thank you for trusting me Mr Dan Fogelman with being your young Randall.’

Niles, who plays teenage Randall (before Sterling K. Brown portrays him as adult Randall), commented: ‘Loved every single moment we’ve had,’ adding: ‘Can’t wait for the memories we make in the future!’

In the series of snaps, Lonnie posted other pictures of all the Randalls together, including Sterling, who stars alongside Justin Hartley and Chrissy Metz as the adult ‘Big Three’.

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The poignant finale left viewers in floods of tears as The Big Three mourned their mother.

The tear-jerker episode saw the family promise they would not drift away from each other as they reflected on the lessons Rebecca had taught them growing up.

Throughout the episode, The Big Three were seen as young children before jumping to the present where they were making preparations for their mum’s funeral.

This Is Us aired on NBC and is available to watch in the UK on Disney+ and Amazon Prime.

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