GET ready to call Marie Osmond “Grandma”!

Her eldest son, Stephen Craig, has finally made good on his promise to give his superstar mom her first grandchild!

A source close to MARIE, 53, tells The ENQUIRER that Stephen’s wife, Claire, is three months pregnant – and they’re praying it’s a boy.

That’s because, as we reported in 2011, the parents-to-be hope to name their son Michael – as a tribute to Ste­phen’s adopted brother who committed suicide at age 18.

Michael had been suffer­ing from depression when he jumped from the eighth-floor balcony of his Los Angeles apartment building in Febru­ary 2010.

“Needless to say, Marie was absolutely devastated by Michael’s death,” said the source.

“That’s why finally becoming a grandma means so much to her. It’s bringing a measure of joy back into her life.

“Marie said, ‘I can’t wait! You won’t be able to get me away from that child!’”

Stephen, 30, wed Claire Olds, 29, in a Mormon cer­emony in Newport Beach, Calif., in September 2011.

“Marie was deeply touched when Steve told her the baby news,” said a source.

“He also told his mom that, if it’s a baby girl, they’ll name her Olive in honor of Marie (whose first name is Olive) and her late mother Olive, who died in 2004.

“Marie said, ‘It doesn’t matter if it’s a boy or a girl. Simply having a grandchild would be the greatest gift that Steve and Claire could possibly give me.’ ”