At the sentencing, a judge described him as a "shark swimming in the waters of the internet... preying on children".
Stothard also had to sign a Sexual Harm Prevention Order, which will prevent him from living with any person under 18 and allowing police to monitor his internet use.
Police became aware of the sex offender after concerns were raised about him trying to contact a vulnerable girl in the Bristol area.
Officers working on Avon and Somerset Police's Operation Topaz then seized his electronic devices, which revealed the extent of his sick crimes.
The investigation also led to the arrest of another man who has since been jailed for four years for child sex offences.
Owen Hall, 26, from Hartcliffe, Bristol, groomed the same 14-year-old Bristol girl targeted by Stothard and incited her to engage in sexual activity.
Detective Constable Kim O'Donnell said: "Clinton Stothard is a predatory paedophile who masqueraded as a 19-year-old and used a variety of aliases as he befriended and groomed his victims.
"Such was the extent of his deceit that he effectively groomed one girl's entire family – winning their trust so much they felt comfortable taking him on holiday.
"The intensity of his grooming was quite frankly shocking, with another of his victims bombarded with thousands of calls and texts over a short period of time.
"I hope the sentence handed down by the court goes some way to providing all those he preyed on with some sense of closure and that this case sends a message to those who commit such crimes, that we are committed to protecting the most vulnerable members of our society and geography will not be a barrier for us.
"I also want to reassure anyone else affected by this inquiry you can come forward knowing you will be believed, listened to and offered all the support you require."
