The couple divorced in 2015 after almost 20 years together.
In an interview with Vulture, the Spanish actor, 59, revealed how close he remains to the 62-year-old Oscar nominee.
"I am not married with Melanie anymore but she is my family. She is probably one of my best friends, if not the best friend that I have,' he gushed to the publication.
The "Desperado" actor recalled being star struck when he first saw Griffith on the red carpet of the 1989 Academy Awards. He attended the event with Pedro Almodovar, whose "Women on the Verge of a Nervous Breakdown" was nominated for Best Foreign Language Film.
"I saw this blonde woman and I knew her because I saw movies of her, but I didn't remember [her name] at the time. So, I said to Pedro, 'Who is she? Who is she? What is her name?' Pedro said 'That's Melanie Griffith!' I said 'That's it. Oh my God.' Six years later, I was married to her."
The couple share daughter Estrella, 22. Griffith also had two children from two previous marriages, Dakota Johnson, 29, and Alexander Bauer, 34. Banderas fondly recalled the time living as one family, even if it seemed brief.
"Everything happened in those years really fast. My life was fast and fascinating if I actually see it in retrospective. I remember those years as very effervescent and really beautiful. My family is there, Dakota, Little Estella and Alexander."
The blended family even had nicknames for each other.
"Melanie called me Negrito. And I used to call her Rubia," he explained.
"Rubia is 'blonde' in Spanish and Negrito is 'little black boy'. I don't know why she called me that, but she called me Negrito. And Dakota called me Paponio, which is a mixture between papa, which is 'daddy' in Spanish, and Antonio. I am her Antonio papa, so Paponio."
And Banderas is a proud Paponio of Johnson and her success in Hollywood. "I met her when she was five years old! I followed every single step of it. I'm so proud of her. I saw her the other day in Toronto, and she looks... as I said in the social networks when I put a picture of her and myself, I put there, 'My radiant Dakota.'"
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