R&B singer Brian McKnight's son and daughter both went on social media yesterday, to air out their father.

It all started yesterday, when Brian's son - Brian Jr - explained how his R&B singer father "abandoned" him as a child.

Brian Jr told the fans, "I can't imagine abandoning my children." He continued, "It's hard to imagine the psyche of a man who can truly just turn his back on his actual sons."

Brian Jr claims that he still suffers emotional scars from his dad's actions. And Brian Jr is upset, he told fans, "I'm not letting this sh*t  slide."

Here's his full story:

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Then, Brian's daughter Bri McKnight took to Instagram to co-sign her brother. She told fans, "At a very young age, I was always second place in may father's heart. Maybe even third, fourth, or fifth depending on the situation."

Here's her full story:

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Back in 2010 Brian McKnight had to pay a Florida woman 14 years worth of back child support, roughly $341,060, for a 14-year-old son he knew nothing about. Miriam Lee filed paternity and child support docs in Orange County, FL years ago alleging McKnight is the father of her son. Brian never filed docs addressing her claim .. so the judge ruled Brian’s the daddy. At the time Brian’s monthly support payment was $11,388 a month.

A rep for Brian McKnight said at the time, “The judgment in Florida was a default judgment made without Brian present. He’s still looking to establish paternity, and is awaiting the results of a recent test.”