Young Sheldon star Iain Armitage had the cutest moment with his onscreen brother Montana Jordan’s daughter, Emma Rae Jordan, as he sang his iconic lullaby, “Soft Kitty” to her.

On his personal social media page, the American actor shared a memorable mini gathering with Montana’s family.

“I finally got to meet my brand new niece! I spent time with Montana and Jenna’s sweet baby and she’s beautiful! I’m not at all biased but she’s the smartest, sweetest, most adorable human and I’m proud to be her Uncle Iain,” he expressed.

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He added, “Montana is getting ready to start filming his new show and I couldn’t be happier for him and his beautiful family.”

Iain then shared how singing Sheldon Cooper’s ‘favorite song when he’s sick’ to babies was actually very effective.

"Soft kitty, warm kitty, little ball of fur! Happy kitty, sleepy kitty, purr, purr, purr," Iain softly sang to Emma.

“Note- I don’t usually sing 'Soft Kitty' to babies but I’m learning that they genuinely seem to like it. Have you soothed your baby with this song?!” he then expressed.

He ended his anecdote by expressing his adoration for his new niece.

“Congratulations, Montana and Jenna and welcome to the world, Emma Rae Jordan! You are very, very loved! ❤️”

Iain and Montana worked together playing brothers in the spin-off prequel series of the popular American sitcom The Big Bang Theory. 

Iain played the young Sheldon (Jim Parsons played the older version in the sitcom) while Montana played the younger version of Sheldon’s older brother, Georgie (played by Jerry O'Connell on The BIg Bang Theory).

Last May, the show bid its farewell after seven seasons after premiering in September 2017.

READ: ‘Young Sheldon’ star Raegan Revord shares last family dinner scene

In a previous post, Iain took a trip down memory lane as he shared a photo of himself on the first day he filmed the series and reflected on his journey on the show. 

"This is 8 yr old me getting ready to film the very first scene I did as Young Sheldon. @melissapeterman recently asked what I would go back and tell my younger self. Maybe I wouldn’t tell him anything and I would just let life unfold as it does, but I think he’d be so surprised and happy to see where we are now. I sure am," he remarked.

READ: ‘Young Sheldon’ star Iain Armitage reflects on journey in the series as it draws to a close

Raegan Revord, who played the role of Sheldon's sister Missy Cooper, also reminisced about her time on the show.

"Over the years, I’ve watched a lot of my favorite shows have their series finales and one thing I always thought about is how heartbreaking it must be to say goodbye, never thinking about my own because it seemed so far into the future. Here I am on the day of my own finale heartbroken," she confessed.

READ: Raegan Revord bids goodbye to ‘Young Sheldon’: ‘I’m filled with wonderful memories and gratitude’

The actress went on: "I love this cast, our incredible crew, and these characters so much not having them in my life everyday seems impossible. But I’m also filled with wonderful memories, a beautiful childhood, a family forever, and gratitude."

Meanwhile, Montana, together with Emily Osment, who played Mandy McAllister, is currently gearing up for their spin-off series titled Georgie & Mandy's First Marriage. The show is expected to air next year.