"I refuse to speak in detail about the nature of my mother's past, or her sexual partners, and I am gravely embarrassed to even be saying this now, but I have been told for most of my life that the white man on my birth certificate is not my biological father and that my actual biological father is a light-skinned black man," he said.
King was answering allegations made this week by websites Breibart.com and the Daily Beast that claimed King's father is white.
Black Lives Matter -- the nationwide rallying cry of activists protesting the killing of unarmed black men by police -- is growing in the limelight and King has been at the center of it, appearing often on television talk shows and at protest sites.
"It is horrifying to me that my most personal information, for the most nefarious reasons, has been forced out into the open and that my private past and pain have been used as jokes and fodder to discredit me and the greater movement for justice in America," King wrote.
A direct question
CNN's Don Lemon exchanged text messages with King on Wednesday night and asked him directly whether he was black or white.
"Initially, he did not answer but later referred to himself as biracial," Lemon said. "But then when I asked him if that's what it shows on his birth certificate I did not hear back from him. No answer on that."
King, in tweets with Lemon, said the various reports are all lies designed to discredit his cause.
"This attack isn't about me so much, but is about derailing Black Lives Matter and the movement against police brutality," he said.
In one of a series of tweets Wednesday, King said, "First off, the key facts about my biological relatives are all wrong. They tried, but my family, like many of yours, is one big mess."
King blasted Breibart, The Blaze, talk show host Glenn Beck and other conservatives, saying they don't care what color he is, they only want him to "shut up."
He also compared his situation to President Obama's "birther" controversy.
"In essence, what is happening to me now, is like conservatives demanding Obama's long form birth certificate," he tweeted.
On Thursday, King wrote: "Never have I once identified myself as white. Not on forms, not for convenience or privilege, and not for fun and games, have I ever identified myself as white. I was never a white guy pretending to be black. Not once, ever, did it occur to me that I was being phony or fraudulent or fake."
One of the allegations made against King is that he misrepresented himself to get a scholarship, financed by media mogul Oprah Winfrey, to get him through Morehouse College, the historically black college in Atlanta. King flatly denied these claims.
"To be clear, I received a full academic and leadership scholarship to attend Morehouse College based on my grades and my leadership skills," he wrote.
"When I was forced to leave Morehouse to have yet another spinal surgery, I lost that scholarship and was then offered a scholarship from Oprah Winfrey when I returned to complete my studies. She wanted it to be for 'diamonds in the rough' and that was pretty much who I was at that point. I didn't apply for it. Nobody does. The college selects brothers who need it and I was, very gratefully, chosen for it," King said.
Morehouse said Wednesday that it had "no comment" on the allegations against King, but added the college doesn't grant admissions or scholarships based on race.
A hate crime?
Another charge against King is that he lied about being the victim of a hate crime 20 years ago when he was a high school student in Versailles, Kentucky.
King said he was beaten by a "racist mob of rednecks" so badly that he missed almost two years of school while recovering from fractures to his face and ribs as well as severe injuries to his spine. A Forbes magazine profile called it "one of the first registered hate crimes" in Kentucky history.
"In March of 1995, it all boiled over and a racist mob of nearly a dozen students beat me severely, first punching me from all sides, then, when I cradled into a fetal position on the ground they stomped me mercilessly, some with steel-toed boots, for about 20 seconds," wrote King.
"I had fractures in my face and ribs, but most badly damaged was my spine. I ended up having three spinal surgeries and missed 20 months of school over it. My entire family endured this deeply painful time in my life ranging from the surgeries, the brutal recovery, physical therapy, and professional counseling. It was rougher than my words will ever do justice."
The Blaze disputes King's claims
, citing police reports and witness statements that describe his injuries as minor and the incident as a fight between him and another person, not a beat down from a racist mob. The Blaze also reported that the FBI didn't have any record of hate crime incidents reported in Versailles in 1995.
King's high school attack was racial, but it wasn't a hate crime, a family member told Lemon. King's family member said the cause of the altercation was about him being a white guy dating a black girl.
King maintained on social media Wednesday that he was indeed the victim of a hate crime.
Does it matter?
If King is lying about his race, does it matter?
Attorney and legal commentator Mel Robbins says it does because it becomes a distraction to Black Lives Matter.
"It matters because (there are conservatives) that would like to discredit the Black Lives Matter movement at all costs," she said. "Every time somebody does this and they're not punished for it, it actually has a negative impact on the bigger movement."
CNN legal commentator Areva Martin agreed, saying the controversy is taking the focus off of the issues the Black Lives Matter movement cares about, like police brutality.
And if King has been lying about his race, Martin said that's extremely harmful to Black Lives Matter.
"This movement cannot be sustained if you have leaders who are not credible," she said. "The public is not tolerant of people who misrepresent themselves. You have to be who you say you are."
King sought to redirect attention away from questions about his race and toward his actual work.
"My work has never been about me and I've never made a big deal about my race. I've actually tried hard to avoid ever making a big deal out of it and have, instead, simply tried to do good work that matters. I'm eager to get back to the cause that concerns me most," he wrote.