In 2011, she took the boy from her mother, who had legal custody, and fled with him to her home in Arkansas, saying she had concerns over his safety.
A judge ordered authorities to pick up the boy and days later authorities found McCready hiding with Zander in a closet at her home.
In addition to her relationship with McKnight, McCready had romances with musician David Malloy and actor Dean Cain -- as well as admitting to an affair with baseball player Roger Clemens, which he didn't confirm or deny.
In 2010, Vivid Entertainment released a porn video called "Mindy McCready, Baseball Mistress" that featured McCready having sex with a boyfriend 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," 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 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 tweet 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 night, on the porch of her home, she changed her mind.