One day after former NBA star Dwyane Wade and Gabrielle Union opened up about their 12-year-old's gender identity, Wade's older child, Zaire, shared a heartfelt message to his sister.

Zaire, who is five years older than Zaya, wrote that as a child, he begged his mother [Wade's ex-wife Siohvaughn Funches] for a brother because he was "looking for company and someone to look after and take care of."

Since Zaya's birth in 2007, the two have been inseparable, and after his younger sibling revealed to him that she is a female, Zaire assured her, "There's no love lost on this side."

"I have been blessed to have my best friend, Zaya with me for 12 years. We did everything together...we fought, we played, we laughed and we cried. But the one thing we never did was leave each other behind," Zaire wrote alongside a childhood photo. "I’ve told you that I would lay my life down to make sure you are ten toes down and happy on this earth. I don’t care what they think Z, you are my best friend and I love you kid."

Late last year, Wade, 38, shared in an interview with former NBA players Matt Barnes and Stephen Jackson that nine years ago, he began having conversations with Union, 47, about Zaya's gender identity. The reality of having a child who's part of the LGBTQ+ community forced him to examine his own biases and reconcile how he deals with them, he said.

"I’ve watched my son, from day one, become into who she now eventually has come into," he recalled. "Nothing changes with my love. Nothing changes with my responsibilities. Only thing I gotta do now is get smarter and educate myself more. And that's my job."

In a recent appearance on "The Ellen DeGeneres Show," Wade added that his family members have become "proud allies," with Union even reaching out to the cast of "Pose" to "figure out as much information as we can to make sure that we give our child the best opportunities to be her best self."

"We take our roles and our responsibility as parents very seriously," he explained. "When a child comes home with a question, when a child comes home with an issue, when a child comes home with anything, it's our job as parents to listen to that, to give them the best information that we can, the best feedback that we can -- and that doesn't change because sexuality's now involved in it."