What happens in the Supreme Court this week on same-sex marriage may end up being, like so many things in Washington, about whom you know.So no wonder marriage equality activists were thrilled to learn that Chief Justice John Roberts not only has a cousin who is a lesbian but also that she would be in the courtroom this week with the partner she longs to marry.On Tuesday, the court heard oral arguments on California's ban on such unions. Today, the court will tackle Congress's decision to withhold federal recognition of legally married same-sex couples.The science of polling tells us that the very existence of the cousin is a good thing for advocates of same-sex marriage.About 14 percent of Americans, according to a recent Pew study, say they've changed their minds about gay rights and same-sex marriage because they have a close friend or family member who is gay.The sad fact is, that's about the best most of us can do, as humans.Just ask Sen. Rob Portman, R-Ohio, who spoke out this month as a supporter of marriage equality not because it's the right thing to do or that it's only fair, humane and patriotic to allow everyone life, liberty and the pursuit of happiness. Nope, he became the vanguard Republican supporting gay marriage because his son is gay.Or how about former Vice President Dick Cheney, who had a change of heart (sorry about that, couldn't resist) that "people ought to be free to enter into any kind of union they wish, any kind of arrangement they wish" because his daughter, Mary, is a lesbian. She married her partner, Heather Poe, last year in the District, where gay marriage is legal.Ron Henderson, who lives in Fredericksburg, Va., understands this.He is not an elected official or a big Washington muckety-muck, just another dad who understands that the evolution of folks like Cheney, Portman and himself is the most common way for humans to overcome their biases.His son came out to him in 1976, when acceptance was a little harder.His son was 14, and Henderson was an avowed and vocal homophobe at the time, he said.After he came out, "he cut his wrists, literally, and wrote me a letter in his own blood and ran away."Holding on to the unbreakable thread of a father's love, Henderson stood by his son through years of reckless living, the happiness and stability of a long-term partner, an HIV-positive diagnosis and eventually his death from AIDS in 1993.Now, at 74, Henderson is an advocate who speaks in support of marriage equality.Sometimes, old childhood friends back in South Carolina ask, "How did a redneck like you become such a liberal?" Henderson knows his son was the beginning of that process.So is that what it takes?Not always. Rep. Michele Bachmann, R-Minn., remains firmly anti-gay despite having a lesbian stepsister, Helen LaFave. Conservative activist Phyllis Schlafly has a gay son and has never changed her position on equal rights for the LGBT community.Jean Podrasky, the chief justice's cousin, said she believes he will do the right thing."I know that my cousin is a good man," Podrasky wrote in a guest column for the National Center for Lesbian Rights."I feel confident that John is wise enough to see that society is becoming more accepting of the humanity of same-sex couples and the simple truth that we deserve to be treated with dignity, respect and equality under the law."But shouldn't we hope that all of our leaders -- elected and appointed -- have enough intelligence and empathy to believe every American deserves dignity, respect and equality? Regardless of whom they know?We can only wish.Petula Dvorak is a columnist for The Washington Post.