Cyndi Lauper's Son Declyn Allegedly Sexually Assaulted Woman, New Lawsuit Claims

Cyndi Lauper's son, rapper Declyn "Dex" Lauper, sexually assaulted a woman in a New York City apartment after she refused to perform oral sex on him ... at least according to a new lawsuit.

The suit, obtained by TMZ, alleges Dex invited the woman over in November 2020 and sent her money for private car transportation ... but when she arrived, she claims he "seemed agitated," and they disagreed about her performing fellatio.

She says when she insisted on leaving, Dex took her phone and threatened to break the device if she did not perform oral sex on him. She claims he pushed her onto his bed with his genitals exposed, held her arms down, and forcibly smothered his genitals over her mouth.

The woman also claims Dex called her a "bitch" and a "n****" and told her no one would believe her if she ever repeated what happened between them.

Dex is not being sued for the alleged sexual assault ... instead, the woman is suing Cyndi's husband, David Thornton.

The woman claims David enabled the alleged sexual assault because he leased the penthouse and "knew of his son's violent and sexually abusive propensities, including prior sexual violence against women and prior settlements of claims for similar conduct."

She claims Dex's ex, "Love & Hip Hop: New York" star Brittney Taylor, made public claims in 2018 alleging Dex was physically and verbally abusive during their romantic relationship ... and she says David knew about the allegations but "failed to take any action to supervise, restrict, or prevent his son from using the Premises to perpetrate sexual violence."

The woman says she suffered physical injuries, pain and suffering, emotional distress, humiliation, embarrassment, stress and anxiety, loss of self-esteem and self-confidence, and emotional pain and suffering as a result of the alleged sexual assault ... and she's going after Cyndi's husband for damages.