Layton Poore, 20, struck up a relationship with Mia Livingstone after they met on a night out in London, but he quickly became “aggressive and controlling” towards the teenager and her mother.
Ms Livingstone, then 17, said Poore burned her arm with a cigarette lighter during their short-lived romance, accusing him of repeated bouts of violence which left painful bruises.
She tried to distance herself from Poore, Harrow crown court heard, and ultimately called the police who came to arrest him.
“He made threats to her, saying he was going to harm her, going to kill her, and going to kill her family,” said Nicola Merrick, prosecuting.
“He said he was going to cut her father’s penis off, he was going to come to the house and injure her and her family, and also destroy the family home.”
Poore, from Glen Parva near Leicester, admitted charges of assault occasioning actual bodily harm and witness intimidation, and was sentenced to 31 weeks in prison.
Judge Lana Wood also imposed a three-year restraining order, banning Poore from contacting Mr Livingstone, 77, his wife Emma Beal, and daughter Mia, 18, as well as banning him from visiting their home in Cricklewood.
In an impact statement, Ms Livingstone said she worries for her safety and “cries uncontrollably”, telling the court: “He used to hurt me all the time, punching me, leaving painful bruises on me, he spat on me.”
Ms Merrick said Ms Livingstone and Poore met at a club in Tottenham Court Road. “They hit it off quickly, and Mia took the defendant to her family home, where she lives with her parents,” she said. The assault happened on February 13, when the couple were at the Livingstone home with other young people.
“They were smoking and he was using up her cigarettes,” said Ms Merrick. “When she indicated she wasn’t particularly happy that he was smoking her cigarettes, he held a lighter onto her right arm, causing a burn mark on it.”
Ms Merrick said Poore “insinuated himself” into the Livingstone family life, “dominating not just Mia but also her mother”, and he turned to violent threats when she tried to push him away. “There were threats to kill and behead her,” she said.
“He said he was going to put her head and members of her family’s heads on sticks and to kill her family and to castrate her father.”