Andrew White, of Western Road, Shoreham, was sentenced at Chichester Crown Court after being convicted of sexually assaulting two girls when they were aged 14 or under.
The court heard White had systematically abused his stepdaughters, with allegations against him including touching one of the girls in the bath, kissing one inappropriately on the mouth, inappropriate touching and making one of them touch his genitals.
White, a former mechanic, was found guilty of seven counts of indecent assault against his younger stepdaughter, who now lives in Worthing, in September. The assaults took place in 1995 when the girl was only 10 years old.
White was cleared during the trial of allegations of rape against the older stepdaughter.
In a turn-around on White, 53, pleaded guilty to three counts of assaulting the elder stepdaughter, who now lives in Rustington, when she was 12, 13 and 14.
Four other charges of indecent assault will lie on file.
Prosecutor Sarah Lindop said the older stepdaughter had left home “at the first opportunity she could” after suffering abuse on a “fairly regular basis”.
Beverley Cherrill, representing White, said she hoped his guilty pleas this week would give his victim peace of mind, adding: “She can go away knowing she has been believed on the allegations he has pleaded guilty to.”
She described her client as a “model prisoner” who was set to become a mentor for other prisoners.
The two girls worked up the courage to report the incident in 2008 after they both confessed to each other the sexual abuse they had suffered as children.
Judge William Wood QC said although the offences had happened a long time ago, they had serious consequences for each of the victims.
He said: “You have sexually assaulted children who were in your care when you joined their family.”
Judge Wood QC said he did take into consideration White changing his plea in relation to the older stepdaughter before another trial was needed.
He added, though: “The fact is both these children as adults have been required to worry about this, come to court, give evidence and face cross-examination because you did plead not guilty from the outset.”
Sex offenders register
White was jailed for two years for each stepdaughter he sexually assaulted, with the sentences running consecutively. White has already served 140 days in prison.
Judge Wood QC said he would have to serve more than half his sentence behind bars. White was given a sexual offences prevention order, banning him from any unsupervised contact with a female aged under 16 from having a female under the age of 16 in his home or place of work.
The order also banned him from making any contact with his two victims. His name will remain on the sex offenders’ register for the rest of his life.
White’s eldest victim speaks about her horrific experience in the Thursday, February 24 editions of the Worthing Herald, Shoreham Herald, Steyning Herald and Littlehampton Gazette.