As we're sitting down to lunch at a restaurant in Washington DC, a smartly dressed man approaches Candace Gingrich-Jones. "I just wanted to say hello," he announces, cheerfully, "because I know your brother."
Ms Gingrich-Jones has two stock responses to people who greet her in this fashion. The first, to those who seem friendly, is to politely say how nice it is to make their acquaintance. The second, to anyone who claims to be among her famous half-sibling's enemies, is to smile archly and respond: "You are not alone!"
This time, given the man's ownership of an array of Republican sartorial props (blazer, tie, sensible haircut and stars-and-stripes lapel badge) she goes with the former.
Ms Gingrich-Jones's half-brother is, of course, Newt Gingrich, the former Republican leader in Congress and would-be presidential candidate who is attempting, with mixed success, to position himself as the conservative alternative to Mitt Romney.
The reason for her mixed reactions is that while Newt is among the best-known figures on the right of American politics, Ms Gingrich-Jones is a creature of the left. She also happens to be a lesbian, a mortal sin in the eyes of mainstream Republicans. And she is also a happy participant in same-sex marriage, something every major GOP candidate, including her own half-brother, would like to see outlawed.
But the biggest sore thumb is Ms Gingrich-Jones's day job. As the head of "youth and campus outreach" at the Human Rights Campaign, a lobbying organisation devoted to gay and lesbian issues, she is a professional agitator against the very social values her elder half-brother espouses.
Regardless of whether Newt Gingrich ends up as the GOP contender in November's election, Ms Gingrich-Jones will be working tirelessly to ensure victory for his opponent, Barack Obama.
"No matter who the Republican candidate is, I will do everything I possibly can to ensure they don't win," she says. "President Obama has done so much for the gay community. From repealing 'Don't ask, don't tell', to getting a hate-crime prevention act passed in 2008, to anti-discrimination policies in the workplace, to laws giving gay couples hospital visitation rights. It would be a disaster if he were to lose."
Newt has failed to utter a word about his sister on the campaign trail so far. But Ms Gingrich-Jones has been less discrete. Before Christmas, she popped up on the Rachel Maddow programme to formally endorse Obama. And speaking to The Independent last week, she admitted to being deeply upset by his recent pronouncements on gay issues.
Though stressing that their relationship is "respectful", Ms Gingrich-Jones was perturbed by an interview in which Newt said society should "tolerate" homosexuals in the same way that it tolerated alcoholics. "Does he take these positions because he absolutely believes them? Or does he have them because he's a Republican running for president?" wonders Ms Gingrich-Jones. "Only Newt knows the answer to that. I honestly don't know if that's what he feels in his heart... Politics, it changes people."
Ms Gingrich-Jones puts Newt's position on the hostile end of an array of GOP candidates she believes are playing the homophobic card in an effort to woo the religious right. Recent weeks have seen Rick Perry produce an anti-gay campaign video, and Rick Santorum declare that if America were to legalise same-sex marriage then it should also make polygamy legal and allow men to marry farmyard animals.
"Santorum, Rick Perry and my brother are all in the same bit of the spectrum on gay issues," Ms Gingrich-Jones says, adding that if she had to choose a Republican president it would probably be Mitt Romney. "He supported workplace discrimination protection, when he was governor of Massachusetts. But he won't acknowledge that now."
Ms Gingrich-Jones has never been exactly close to Newt, who at 68 is 23 years older than her, and had left home before she was born. Their genetic relationship is also complex: the duo share a mother, Kathleen. Ms Gingrich-Jones's father, Robert, was Newt's adoptive (but not biological) father.
As a child growing up in Harrisburg, Pennsylvania, Ms Gingrich-Jones only occasionally saw Newt, who at the time was a college professor in Georgia, on the first of his three marriages. "A lot of people see the distance between my brother and me and think it's all ideological; that the reason we don't hang out is because we don't get along," she says. "But, really, he was gone before I was even born, and I never got to know him."
Ms Gingrich-Jones realised she was gay as a teenager, but her first same-sex relationship had to wait until university. There she discovered that several fellow members of the women's rugby team (she plays hooker) were openly lesbian. "Not all lesbians play rugby and not all rugby players are lesbians. But there's a great deal of overlap. And on my college team, I began seeing people that felt what I felt, and were open and fine with that. It was like a piece of my life falling into place."
Ms Gingrich-Jones "came out" in the summer of 1987, when Kathleen discovered a gay newsletter in her bedroom. At the time, Newt was a junior congressman. "I asked what my brother had said about it, and my mother told me that his reply was along the lines of this is my life and I can live it however I want to,'" she recalls.
After university, she settled into an unremarkable job loading trucks for UPS. But her life changed in 1994, when Newt, a rising Republican star, was elected Speaker. "Suddenly, the media became interested in our family," she recalls. One day, a reporter came to interview her. "Towards the end of our conversation, she said: 'I have one more question: are you gay?' I didn't have any reason not to tell her, so I said yes."
With that, she became headline news. Reporters began examining Newt's record on gay issues. It turned out to be surprisingly hard-line. "Until then, I had no idea that he'd said some of the things he said."
Shortly afterwards, the Human Rights Campaign rang Ms Gingrich-Jones. Saying she had a "powerful" story that deserved to be shared, they persuaded her to embark on a tour of the US, holding town-hall meetings at which she counselled people who had been abused or discriminated against because of their sexuality. She later joined the organisation full time, moved to Washington DC, and has been there ever since.
In the glare of publicity that came with the Clinton era, her relationship with Newt became understandably strained. But in recent years, as media attention has waned, it has thawed significantly, she says. Two catalysts for their rapprochement have been Rebecca, Ms Gingrich-Jones's spouse, whom she met in 2006 through her rugby team, the Washington Furies, and Newt's third wife, Callista, whom he married in 2000. "Rebecca is strongly family orientated. To her it was just unacceptable that I would have a blood relative in the same city and we wouldn't do things together. Callista was very much the same. So in the past five years I have seen my brother more than in the previous 25 years. Callista has changed him, made him far more appreciative of family."
Newt and Ms Gingrich-Jones now get together every Christmas holiday. On social occasions, Ms Gingrich-Jones and Newt never talk politics. Instead, they find common ground discussing family matters or American Football.
Ms Gingrich-Jones says her brother is no longer the volatile figure of the 1990s, though she does keep hearing commentators wondering: "When is he going to have his big meltdown?"
Because he has publicly remained hostile to gay rights, Newt's relationship with his sister has its limits. Two years ago, when Ms Gingrich-Jones married Rebecca in Boston, Newt and Callista sent a gift. But they declined an invitation to the event itself, saying they were travelling in Asia.
In future, the limits of his tolerance may be tested further: Ms Gingrich-Jones and Rebecca are planning to become parents, once they have worked out the logistics. So could a lesbian family one day be house-guests in a Gingrich White House? In this most topsy-turvy of sibling relationships, stranger things have probably happened.
Straight Talkers: Candidates' Views
"I believe that marriage is between a man and woman... and I think this [homosexuality] is a temporary aberration that will dissipate. I think that it just fundamentally goes against everything we know."
"...from the very beginning in 1994, I said to the gay community, I do not favour same-sex marriage..."
"Obviously gay marriage is not fine with me."
"[Marriage is] the union that causes children to be born and raised in an environment that's a birthright. When we deny children that birthright by saying other types of relationships are OK, I think we are harming children."