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Sharon Osbourne often tells it like it is, and she didn't hold anything back in an open letter she wrote to her estranged brother, David Arden, and posted on her Facebook page earlier this week.

"The Talk" co-host accused Arden of trying to "make money off" her son Jack Osbourne's 2012 multiple sclerosis diagnosis by selling an article to Britain's Mirror.

"That's as low as it gets, making money off my son's MS," Osbourne, 61, wrote in a Facebook post Tuesday. "Jack was diagnosed in 2012, where have you been the last 18 months? You know how to reach me. You know how to reach the Osbournes."

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Arden, 62, has MS himself. He told the Mirror that he's "the only other person in the family" with the disease.

"I know when I was first diagnosed I wanted to speak to fellow MS sufferers," he said, adding, "I'm sure Jack feels the same."

But Osbourne insisted Jack, 28, had a strong support system.

Addressing Arden in the open letter, Osbourne wrote, "He [Jack] is a married man with a daughter and a loving family. You were only in his life for a handful of years, [Jack] doesn't know you."

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Osbourne went on to list a number of ways she tried to help Arden out financially, saying she "realized after all these years that I cannot buy your respect or love."

She also responded to his claims in the Mirror article that she bad-mouthed their parents, listing examples of how their father, the late music producer Ron Arden, allegedly used her as a "financial shield" and how she "spent years paying off his bills because they were in my name."

Osbourne also addressed Arden's statement to the Mirror that he's "prepared to make peace with her for the sake of Jack."

While making it clear that she's not interested in reconciling with her brother, she wrote, "I really do wish you and your family well."

ABC News was unable to reach Arden for comment.