"For us, we are excited to be welcoming our grandson soon, and providing everything he will need in life while encouraging Georgia to keep her education on track and continue to achieve her goals in life."
Georgia told her story in an open letter to help other girls in the same position.
"I made the decision to grow up too quickly, but I thought it was okay because everybody else was doing it," she wrote in the Weekend Herald.
"It doesn't matter if your world is falling apart and you feel like every day that goes by is only getting worse," she added.
"There is a life that is relying on you, and no matter who stares, who judges, who talks, the fact that you're staying strong for that child is success."
More than 360,000 people viewed the story on the Herald's Facebook page.
"We've had a few chuckles. She's had a few little tears about it," Rob told the Herald on Sunday.
"But she's obviously grown up enough to know that people are going to think what they think — and she's dealing with it very well."
He said the family knew it wouldn't be easy sharing their story with the public.
"It's been a very tough emotional rollercoaster for everyone involved.
"But if this can ... reach out to one person and maybe help them out, I think it's done its business."
Rob said probably 70 per cent of feedback was positive.
Negative comments on social media, which seemed disproportionately from men, included accusations the letter "glorified" teen pregnancy.
"I admire you for supporting your daughter through this whole experience while many other parents could have completely turned their back on the whole situation," Roxana Aedo wrote.
"Age does not in itself make a good or bad parent," Niki Logan wrote. "I think Mason has a pretty good chance in life."
"Ignore the negative, use whatever you need to get where you need to be, and aim high," Grant Turuwhenua posted. "It's going to be a lot of work, but bitter work yields sweeter fruits."
Rob told the Herald on Sunday that the family certainly debated how to approach the pregnancy early on, but now, with Georgia 36 weeks pregnant, family all had their "100 per cent supportive" hats on, he said.