The doting older brother was pictured in rare candid snapshots taken by Heidi at their family home in Los Angeles, as he stood on a ladder to add pink decorations onto the ceiling, as well as filling the room with helium balloons.
The pictures also gave a glimpse inside Heidi's beautiful home, featuring an array of indoor plants and a photo wall going up the stairs.
Heidi and her husband Tom Kaulitz live with her three youngest children in Bel Air, in a gorgeous gated mansion. Heidi's oldest daughter, Leni, 19, lives in New York City, where she is studying.
The family are incredibly close and Heidi often goes to visit Leni in NYC, and most recently reunited with her daughter on the runway at an event in Berlin for Intimissimi, the lingerie brand both mother and daughter work for.
The pair were launching their latest campaign for the fashion label and enjoyed a lavish sit down dinner in the German capital with special guests.
It's safe to say the pair had an amazing time, and Heidi took to Instagram to share some behind-the-scenes photos shortly after the event.
She wrote alongside them: "Thank you @intimissimiofficial for the most magical night in Berlin CELEBRATING our new CAMPAIGN…. and thank you to everyone coming out and spending the evening with us."
Heidi and Seal are also parents to 18-year-old son Henry, who recently delighted his famous dad after driving to his house late at night to crash on the couch. Seal shared a photo of Henry asleep on his sofa, and wrote alongside the picture: "Seems like it was only yesterday I was changing this one’s diapers. Now 18yrs later he drives up to our home, lets himself in and crashes on the couch.
"As a parent you only dream of these moments, for they’re few and far between. I love you son."
While not much is known about Heidi and Seal's youngest three children - who have been largely kept out of the spotlight by their famous parents during their childhoods - Leni is an up and coming model following in her mom's footsteps.
Seal - who adopted Leni when she was a baby - opened up about his close bond with his oldest child during a red carpet appearance with Leni in 2021 for the premiere of The Harder They Fall.
He told Entertainment Tonight of their close bond: "It's always been like this, from the day I met your mother. She [Heidi] was two weeks pregnant with this beautiful woman. We have always had this bond."
In May, meanwhile, Seal made a rare TV appearance on GMA3, where he opened up about his four children and admitted that none of them listen to his music! He also revealed that none of his kids were likely to follow in his footsteps in the music industry.
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