In addition to her relationship with McKnight, McCready had romances with musician David Malloy and actor Dean Cain; she also said she had had an affair with baseball player Roger Clemens, which he didn't confirm or deny.
But Clemens did issue a statement Monday from training camp with the Houston Astros in Kissimmee, Florida. "Yes, this is sad news," he said. "I had heard over time that she was trying to get peace and direction in her life. The few times that I had met her and her manager/agent they were extremely nice."
In 2010, Vivid Entertainment released a porn video called "Mindy McCready, Baseball Mistress" that featured McCready having sex with a man referred to as "Peter" and talking about her exploits with Clemens.
Sunday night, country music stars offered their condolences as they learned of McCready's death.
"My heart goes out to Mindy McCready's family. I knew her well," singer LeAnn Rimes said on Twitter. "It's a horrible tragedy. May peace be with her sons."
Carrie Underwood said she grew up listening to McCready. And country artist Terri Clark said she had had some fun times with her "back in the day."
"I hope our society shows compassion and realizes the severity and reality of mental illness, and addiction," she tweeted.
Singer Wynonna Judd posted a series of tweets also calling attention to addiction and mental illness.
"It breaks my heart what addiction continues to take from this life," she said. "Addiction is a disEASE & not a character flaw. When the pain becomes too much, it causes people to want that pain to stop. This is just so unbelieveable & so sad."
In her words
A year ago, McCready posted excerpts of a book she said was upcoming about her life. She acknowledged a difficult upbringing, personal problems and the challenges she faced turning her life around.
"I haven't had a hit in almost a decade," she wrote in January 2012 on her official fan website. "I've spent my fortune, tarnished my public view and made myself the brunt of punch line after punch line.
"I've been beaten, sued, robbed, arrested, jailed, and evicted.
"But I'm still here. With a handful of people that I know and trust, a revived determination, and both middle fingers up in the air, I'm ready. I've been here before. I'm a fighter. I'm down, but I'll never be out."
But Sunday, on the porch of her home, she may have changed her mind.
On Monday, McCready's publicist asked that the family be left alone.
"It is with the deepest sadness we say goodbye to an extraordinary and gifted talent, a daughter, a mother and friend, Miss Mindy McCready," said Kat Atwood in a statement.
"Our attention at this time is devoted to the needs and care of Mindy's family. As Mindy spent much of her life in the public eye, we respectfully request your consideration and sensitivity to enable friends and family this time of 'quiet.' "
McCready's "friends in music" are planning to organize a memorial in Nashville, she said.