Gabrielle Union ‘Can’t Believe’ Zaya Wade Is 15 as She Celebrates Stepdaughter’s Birthday

Gabrielle Union is watching Zaya Wade grow up before her very eyes.

The L.A.’s Finest star, 49, celebrated Zaya’s 15th birthday on Sunday. “I can’t believe you are 15?!?!?!?!?” Union wrote in an Instagram Story, sharing a recent photo of the birthday girl modeling a Stella McCartney look.

She and Zaya previously spoke to PEOPLE about how their mother-daughter bond has grown so strong. “In a nutshell, time,” Union said earlier this month.

“I think as a stepmom, it’s not my job to push myself into her life or force anything,” she added. “So, time has allowed our bond to grow organically and naturally. Being consistent with each other and being trustworthy with each other also.”

Union also explained that Zaya coming to terms with her gender identity helped them become closer over the years since marrying Zaya’s dad Dwyane Wade in Aug. 2014.

Gabrielle Union ‘Can’t Believe’ Zaya Wade Is 15 as She Celebrates Stepdaughter’s Birthday. https://www.instagram.com/gabunion/

“Zaya coming into truest self did help because I am able to bond with who she actually is versus the representative that was speaking for her for years. Now, she is completely herself and so I know her, not her representative,” Union added.

Zaya echoed her stepmom’s sentiments: “Me discovering who I am, has definitely deepened our bond and also other people’s bonds.”

“I can be truthful and honest with myself and therefore, truthful and honest with other people. That helps better everyone’s connections and relationships with each other,” she added. “Our relationship has grown so much from the first day I met her to now. It is because time has allowed us to grow together and progressively.”

Union and Wade, 40, also share 3½-year-old daughter Kaavia James. Additionally, the retired NBA player is father to sons Zaire, 20, and Xavier, 8, from previous relationships, and he’s served as legal guardian to his nephew Dahveon Morris, 20.