A demented ex-boyfriend sent his former girlfriend’s kid brother a sex tape — starring his big sister.

Angry after the split, Gary Whicker, 22, of Merseyside, England, decided appropriate revenge would be to send the 10-year-old boy the lewd recording, The Mirror reports.

The young boy, who luckily did not recognize his sibling, told his mom about the “naughty” video, and she reported it to authorities after she realized the X-rated vid featured her daughter.

Whicker, who pleaded guilty to disclosing private sexual images with intent to cause distress, will spend eight months in jail for “humiliating” his ex.

“I knew what kind of person he was but I never thought he would stoop as low as he did,” the victim’s mom told the court.