Johann Aguilera told America's Star magazine: "Christina's grandfather is 86 and her grandmother is 82. They have health issues.
"I don't know how much longer they're going to last. Time is running out."
Her grandparents would especially love to see Christina's four-year-old son Max, whose father is 'The Voice' star's ex-husband Jordan Bratman.
Johann added: "I know how much joy it would give my parents if she came back into our lives again."
Christina, 31, made the decision herself to sever contact with her dad Fausto - a US army sergeant - in 1999.
The musician has accused Fausto of hitting her mother Shelly - who separated from him when Christina was just seven - during their marriage and she has recorded the songs 'I'm OK' and 'Oh Mother' about her difficult childhood.
In February, Christina did indicate she might be prepared to give her father another chance and reconcile her relationship with him.
She said: "I've talked about how rough things were for me and I'm sure he's heard it. He can't be thrilled about it. So maybe one day we can do lunch ... I'm 31 years old now. Maybe it's time."