Mark Evans walked out on the 'Someone Like You' singer when she was just three years old and has had a turbulent relationship with her since, but he has now expressed hope of becoming "a big part" of his grandchild's life.
On hearing of Adele's pregnancy from his mother, Evans told The Mirror: "I would have loved so much to have been able to hold her in my arms and tell her how happy I was for her.
"I want more than anything to be part of her life again and to be a big part in my little grandson or granddaughter's life. I'm having to face up to the fact that I may never get to know my grandchildren and it is breaking my heart."
The 50-year-old did admit, however, to being concerned that Adele has not been with partner Simon Konecki long enough to have a baby with him.
"I wish Adele and Simon had been together longer," he said. "I was the same when I was, coincidentally, pretty much the same age as her. No one could tell me anything because I thought I knew it all."
Evans, who also revealed that Adele had wanted four children, went on to explain his reasons for being "a rotten father" to the 21 star.
"I guess now I'm paying the price. A day doesn't go by when I don't wish I could change things," he said.
"I know I've been a drunk and a self-pitying fool but my heart was broken at the time and booze was the only thing that made the pain go away.
"I am begging her to give me another chance... It breaks my heart to think I might not see her in the years ahead or hold my little grandchild in my arms."
Speaking in February, Adele stated that Evans had "blown" any chance of a reunion and vowed: "He will never hear from me again."
"There's consequences other than just getting a bit of f**king money that lasts you half a year," she said of his appearances in the press.
"It blows my mind. 'I love her so much'. Really? Why are you telling me that through a newspaper? If I ever see him, I will spit in his face."