Tell us, Barbara Bush (search), just what is "Sex and the City"?

"I don't know, what is 'Sex in the City'? the 79-year-old grandmother replies.

"I'm too old," says her husband, former President George H.W. Bush.

Barbara Bush then adds, "Same as in the country, isn't it?"

Their twin granddaughters, Jenna and Barbara Bush, teased their grandmother about not being hip Tuesday night when they spoke at the Republican convention. "She thinks 'Sex and the City' is something married people do but never talk about," Jenna told delegates.

Barbara Bush may have been joking about whether she was familiar with the ribald television series when interviewed by ABC's "Good Morning America," but she readily acknowledged that she is more likely to lay down the law with the twins than either her husband or the twins' own parents.

"George is putty in their hands, and I'm the one who's saying — not just to them — pull down your skirt or put on a skirt or pull up your top or something. That's just part of me, can't help it," Barbara Bush said in an interview broadcast Thursday.

"They rule by gentleness," she said of the twins' parents, President Bush and first lady Laura Bush, "other than my socking, shouting, yelling."

During the twins' convention appearance, the former president wagged his finger at them as they went on a comedic riff about their parents and grandparents. It was all in fun, he said.

"We tease each other," Bush said. "They're wonderful girls, they really are."

The former first lady recalled receiving a letter from someone she knows saying she should tell Jenna Bush how outrageous it was for her to have stuck out her tongue at photographers while traveling with her father on a campaign trip, an act caught on film.

"I wrote the girl back and I said, if you'll pardon me, 98 percent of Americans would like to stick their tongue out at the press," Barbara Bush told ABC, adding that the gesture took place while the press corps was kidding around. "It was so nothing, and it was funny."