Michael Lee Clarkson, 27, of Greenset Close, Lancaster, has been jailed for seven years after admitting inciting a child to enagge in sexual activity.
Judge Philip Parry also imposed a 10 year sexual harm prevention order (SHPO).
Preston Crown Court heard Clarkson’s first victim was “an insecure and vulnerable young girl” who he spoke through her online X-Box account as she played Grand Theft Auto 5.
He continued contact with her despite being warned off by her older brother when he discovered they were in contact.
Emma Keogh, prosecuting, said he had displayed jealousy and obsessive behaviour towards both, and had also ‘proposed’ to the victims.
Referring to the 13-year-old she added: “Her family noted a change in her behaviour, her mum remarked she was becoming secretive and acting out of character.
“Her brother sent a message that his sister was only 13 and that it was completely inappropriate for him to be contacting her. He recalls the Frosty nickname which he adopted in his online persona.”
The court heard the girl had a Facebook account in another name in which they had exchanged messages.
Her mum later found a message suggesting they meet in the summer holidays and have sex in the changing rooms of a swimming pool.
In an interview the girl revealed he had carried out sexual acts over a video messenger, and encouraged her to do the same.
Ms Keogh added: “ The effect on this child is profound. Above and beyond the embarrassment and discomfort of performing the acts, she has explained she self harmed because she felt she was guilty and shouldn’t have done it, and felt sorry for her family having to read their exchanges.”
Referring to internet evidence she added: “There could be no doubt the individual with blue hair and distinctive snake type piercings could be the defendant.”
Clarkson also admitted engaging in sexual activity with a 15-year-old girl.
Both youngsters cannot be identified for legal reasons.