The photo she posted on Instagram shows her as a baby beside a young Walker.

“The moment I realized we are twins,” Meadow captioned her post on Saturday. “Happy birthday to the most beautiful soul.”

Walker died at the age of 40 in a fatal car crash on Nov. 30, 2013, alongside his friend and financial adviser Roger Rodas, 38.

The actor was best known for his role as Brian O’Conner in the “Fast & Furious” movie franchise, an action series by Universal Pictures that largely centers around illegal street racing, heists and espionage. Walker appeared in six of the franchise’s movies.

Meadow was 15 at the time of Walker’s death and had been living with him in California for two years after being raised in Hawaii. As a teenager, Meadow was at the center of a custody and inheritance dispute between her mother, Rebecca Soteros, and the Walker family.

In 2014, she was named Walker’s sole beneficiary. A year later, she sued German car maker Porsche claiming that Walker initially survived the crash but was unable to free himself from the seatbelt of the 2005 Porsche Carrera GT, according to Page Six. Meadow and Porshe settled their lawsuit in 2017 for an undisclosed amount.

Meadow, now 21, launched a “do good challenge” in honor of her father this year.

“In honor of my dad’s birthday, I’m kicking off our annual do good challenge,” she wrote in a separate Instagram post. “This year, I’m keeping it simple and close to my heart. I am so blessed to be in love with my best friends.”

Meadow tagged some of Walker’s former co-stars and other famous faces in her challenge, including Vin Diesel, Jordana Brewster and rapper YG.