Ask Candace Gingrich-Jones what people don't know about her older brother, and she'll tell you about his lighter side.

"Like a lot of folks, Newt has a public and a private persona," she said in an interview with ABC News. "He can be a pretty fun person with a fun sense of humor, and the ability to be irreverent."

But when it comes to politics, Gingrich-Jones - a gay rights activist - isn't laughing.

"We're not that different from most families in that we have widely different opinions on a variety of topics," Gingrich-Jones, 45, said. "But I don't support my brother's qualities when it comes to LGBT equality issues. I could not support the campaign of somebody who doesn't think I deserve the same rights as other people."

Gingrich, who is 23 years his sister's senior, opposes same-sex marriage and gay adoption, favors the reinstatement of "don't ask don't tell" for the military, and supports the federal Defense of Marriage Act. They're all positions his sister finds surprising, particularly in light of their longstanding personal relationship, which she characterized as "uncle-niece-like."

"People talk about the LGBT rights movement and they talk about what's had the biggest impact on its progress being more people coming out, and most people who know somebody gay 'get it,'" said Gingrich-Jones. "But no one has asked him about why he doesn't 'get it.'"

The two, who never lived in the same house together, have had regular encounters over the years, joining the extended family at holiday gatherings or on summer trips to the beach or amusement parks with the kids. While they are technically "half" brother and sister sharing the same mother,  Gingrich-Jones said the family never uses the word.

They were most recently together several weeks ago in Washington when the family gathered to hear Gingrich's wife Calista sing in the choir at the Catholic Shrine of the Immaculate Conception.  "We exchanged some chit chat. It was cordial," Gingrich-Jones said.

The elephant in the living room at most of the gatherings, according to Gingrich-Jones, is the fact that she is married to her wife, Rebecca Jones, contrary to the views of her brother.

"He said, 'It's your life and you live the way you want to,'" said Gingrich-Jones, describing Newt's reaction to her coming out at age 21 in 1987. But she soon learned there were caveats.

"Watching his rise as Speaker and learning more about his views and anti-gay opinions, I became much more disappointed," Gingrich-Jones said.

When she wed Jones in 2009 at a ceremony to which her brother was invited, he did not attend because he was traveling abroad.

"I don't know whether the trip was planned before or after the invitation," she said. "But I've known since the 1990s, he's said if I ever had a wedding and married a woman he wouldn't come."  She said he did send a card and shower gift, however.

Gingrich spokesman R.C. Hammond told ABC News,  "Newt loves his sister very much. They have a good relationship."

"A brother and sister bond can handle a difference in political views," he said.

But that doesn't mean Gingrich-Jones is going to spend the 2012 campaign sitting on the sidelines. She is planning to take an active role campaigning for President Obama.

"The things we saw happen in the last four years of the Obama administration would all, or many of them, go away under a President Gingrich. It would be a huge setback," she said.

 ABC News' Elicia Dover contributed to this report.