De Lesseps shared a photo on Instagram of herself embracing Noel. She marked the occasion by lighting birthday candles in several pastries.
"@noeldelesseps proud to be your mom! Happy Birthday my handsome kind boy!" the star captioned the post.
De Lesseps said in an interview with People in August that she had reconciled with Noel and her daughter, 23-year-old Victoria de Lesseps, after the siblings and de Lesseps' ex-husband Alexandre de Lesseps sued her in July.
"Things between my kids and I are going great," the star said. "Everything is cool."
"The story continues between [Alexandre and me], but not the children," she added.
"That's all that matters to me. We'll work things out."
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De Lesseps said during an appearance on "Today" in August that the lawsuit contributed to her relapse in sobriety.
"That was devastating. I felt betrayed. I felt so hurt. I lost it," she recalled.
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