(CNN)Brenda Jackson, mother of Dale Earnhardt Jr. and Kelley Earnhardt Miller, has died of cancer at 65, JR Motorsports announced on Monday.
"I'm glad her suffering has ended and she can be at peace," tweeted Earnhardt Jr. "She would be in tears of happiness over the words of support and remembrance she's been shown today. Our family appreciates it as well. She will live in our hearts forever."
Jackson worked as an accounting specialist for JR Motorsports, owned by Earnhardt Jr, Miller and Rick Hendrick, since 2004 and was known for her wit and charisma.
"Her sarcastic musings and straightforward approach injected a brand of humor at JR Motorsports that became part of its fabric as it grew into a full-time NASCAR racing operation in 2006 and a championship-winning organization in 2014," the company said in a statement.
Jackson enjoyed being able to work alongside her children for the past 15 years.
"I am a very, very lucky woman, as I get to interact with my kids almost every day," she said last year. "I've got two bright, beautiful kids that I am very proud of."
"Kelley's standards are very high. She conducts herself that way and she expects that of everyone else. Dale Jr. just gets bigger and bigger. I am very proud of his accomplishments, but as a mother I am proudest of the way he handles himself with honesty and the way he cares about his family and his friends."
Jackson's journey into the racing world started when she was born. Her father, NASCAR fabricator Robert Gee, built many winning cars, including one for racing legend Dale Earnhardt. She married Earnhardt in 1972 and they had two children, Earnhardt Jr. and Miller.
They divorced several years later and the kids lived with her until they lost everything in a house fire and she signed over custody to Earnhardt. In 2017, Earnhardt Jr. referenced the fire when he read her an emotional letter he wrote her for Mother's Day.
"You, a single mother, us losing everything in a house fire. You gave custody of us two kids to our father, knowing that he could provide a promising future."
"I'm thankful that we are together today, as I am older and wiser to appreciate the sacrifices that you made for us," said Earnhardt Jr. "You never failed at making me feel loved. I love you. Happy Mother's Day, Mom."
Jackson remarried in 1985 to Willie Jackson, a firefighter in Norfolk. When he retired, the two, along with her stepdaughter, Meredith, moved to North Carolina, where Jackson worked for JR Motorsports.
She was preceded in death by her parents, Hazel May Overton Clark and Robert Edward Gee, and her sister Sandra Gee.