By John Blake, CNN

(CNN)– Rev. Martin Luther King Jr. was writing an advice column in 1958 for Ebony magazine when he received an unusual letter.

“I am a boy,” an anonymous writer told King. “But I feel about boys the way I ought to feel about girls. I don't want my parents to know about me. What can I do?”

In calm, pastoral tones, King told the boy that his problem wasn’t uncommon, but required “careful attention.”

“The type of feeling that you have toward boys is probably not an innate tendency, but something that has been culturally acquired,” King wrote. “You are already on the right road toward a solution, since you honestly recognize the problem and have a desire to solve it.”

We know what King thought about race, poverty and war. But what was his attitude toward gay people, and if he was alive today would he see the gay rights movement as another stage of the civil rights movement?

That’s not the type of question most people will consider on this Monday as the nation celebrates King’s national holiday. Yet the debate over King’s stance toward gay rights has long divided his family and followers. That debate is poised to go public again because of the upcoming release of two potentially explosive books, one of which examines King’s close relationship with an openly gay civil rights leader, Bayard Rustin.

The author of both books says King’s stance on gay rights is unclear because the Ebony advice column may be the only public exchange on record where he touches on the morality of homosexuality.

Yet King would have been a champion of gay rights today because of his view of Christianity, says Michael Long, author of, “I Must Resist: Bayard Rustin’s Life in Letters,” who shared the story of King’s Ebony letter.

“Dr. King never publicly welcomed gays at the front gate of his beloved community. But he did leave behind a key for them - his belief that each person is sacred, free and equal to all to others,” says Long, also author of the upcoming “Keeping it straight? Martin Luther King, Jr., Homosexuality, and Gay Rights.”

Did King’s dream include gay people?

One person close to King, though, would disagree.

Rev. Bernice King led a march to her father’s graveside in 2005 while calling for a constitutional ban on gay marriage. She was joined by Bishop Eddie Long, senior pastor of New Birth Missionary Church in Georgia, where she served as an elder at the time. Long, who recently settled out of court with four young men who filed lawsuits claiming he coerced them into sexual relationships, publicly condemned homosexuality.

King did not answer an interview request, but she has spoken publicly about her views.

During a speech at a church meeting in New Zealand, she said her father “did not take a bullet for same-sex marriage.”

Yet her mother, Coretta Scott King, was a vocal supporter of gay rights. One of her closest aides was gay. She also invoked her husband’s dream.

Ravi Perry, a political science professor at Clark University in Worcester, Massachusetts, said King’s widow once said in a public speech that everyone who believed in her husband’s dream should “make room at the table of brother and sisterhood for lesbian and gay people.”

There is no private or public record of King condemning gay people, Perry says. Even the FBI’s surveillance of King’s private phone conversations didn’t turn up any moment where King disparaged gay people, she says.

“If Dr. King were anti-gay, there would likely be a sermon, a speech, a recording of some kind indicating such,” she says. “And knowing how closely his phones were tapped; surely there would be a record of such statements.”

Those who say King did not condemn gays and would have supported gay rights today point to King’s theology.

Though King was a Christian minister, he didn’t embrace a literal reading of the Bible that condemns homosexuality, some historians say. King’s vision of the Beloved Community – his biblical-rooted vision of humanity transcending its racial and religious differences – expanded people’s rights, not restricted them, they say.

Rev. C.T. Vivian, who worked with King at the Southern Christian Leadership Conference, says King would have championed gay rights today.

“Martin was a theologian,” Vivian says. “Martin starts with the fact that God loves everybody, and all men and all women were created by God. He based his whole philosophy on God’s love for all people.”

King’s relationship with ‘Brother Bayard’

Those who say King would have championed gay rights also point to King’s treatment of one of the movement’s most important leaders, Bayard Rustin.

Rustin was an openly gay civil rights leader who is widely credited with organizing the 1963 March on Washington. He was an organizational genius, the man who insisted that King speak last on the program, giving his “I Have a Dream” speech the resonance it would not have had otherwise, says Jerald Podair, author of “Bayard Rustin: American Dreamer.”

“He was the kind of guy who could tell you how many portable toilets you needed for 250,000 people in a demonstration," Podair says. “He was a details guy. King needed him for that march.”

But Rustin could do more than arrange a demonstration. He was also a formidable thinker and debater. He was born to a 15-year-old single mother and never graduated from college.

The movement was led by intellectual heavyweights like King, but even among them, Rustin stood out, Podair says. He read everything and was a visionary. One aide to President Lyndon Johnson described him as one of the five smartest men in America, says Podair, a history professor at Lawrence University in Appleton, Wisconsin.

“People who heard him speak were transfixed,” Podair says.

Rustin became one of the movement’s most eloquent defenders of its nonviolent philosophy, says Saladin Ambar, a political scientist at Lehigh University in Pennsylvania.

“He was one of the few individuals not afraid to debate with Malcolm X in public,” Ambar says. “Rustin more than held his own and really challenged Malcolm to push his thinking.”

Rustin was a special assistant to King and once headed the Southern Christian Leadership Conference. During the planning of the March on Washington, King resisted calls to jettison Rustin because he was gay, Podair says.

King, though, didn’t speak out on behalf of gay rights because he was doing all he could to hold the movement together, historians say.

He had to constantly fend off rumors that the movement was infiltrated by communists. He was also criticized for expanding the movement to take on poverty and oppose the Vietnam War.

“The movement superseded any discussion of gay rights,” Ambar says. “King was dedicated to the cause at hand.”

With all that was going on, King couldn’t afford to wage a public campaign defending Rustin’s homosexuality, says Vivian, a SCLC colleague of King’s.

“Any employee that would employ a gay person at the time who was outwardly gay would have problems,” Vivian says. “I don’t care if you were the president of the Untied Sates, you would have trouble doing that.”

After the 1963 March on Washington, Rustin remained as King’s adviser. The two, however, drifted apart when King became more radical during the last three years of his life, says Adair, Rustin’s biographer.

When Rustin died in 1987, he was starting to receive attention from gay and lesbian activists who linked civil rights with gay rights, Podair says.

Rustin was a late convert to their cause.

“He never put it [homosexuality] front and center,” Podair says. “He never politicized it until the end of his life. He didn’t want to make a big deal out of it.”

It’s no longer unusual today for gay and lesbian activists to draw parallels between their struggles and King’s legacy. Vivian, King’s SCLC colleague, says the comparison is apt.

“There was a time when black people were afraid to be themselves among white people,” he says. “You had to fit a stereotype in order to be accepted. They’re going through the same thing but now they feel better about themselves.”

Vivian says the movement shouldn’t be limited to race.

“As we were freeing up black people, we’re freeing up the whole society.”

Long, author of the upcoming books on King and Rustin, says King’s vision transcended his personal limitations. Maybe he could have said more to that anonymous boy who wrote him at Ebony. But he did leave him a key to the Beloved Community– even if he didn’t realize it at the time, Long says.

Now, Long says, it’s up to those who claim King today to use that key.

“A turn of that key and a gentle push on the gate, swinging it wide open so everyone can enter into the Beloved Community,” he says. “That’s the best way to advance the legacy of Martin Luther King.”