Roman Rarity sexually abused three youngsters when they were aged 11 or 12 and chillingly told one victim: "Don't tell anyone. It's our secret."
Another victim, now aged 34, told the jury at the High Court that Rarity had “ruined my life”.
Rarity, 73, formerly of Seafield in West Lothian, had denied committing three sex offences against the boys.
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But a jury found him guilty of indecent behaviour between 1997 and 1999.
Rarity molested his first child victim on two occasions and the sexual behaviour included carrying out a sex act on the boy.
He exposed himself to a second boy and got him to perform sex acts on him. Rarity also exposed himself to the third child.
Advocate depute Alan Parfery said Rarity had indulged in grooming child victims and told the jury that there was a "pattern of corrupting the innocence of these young boys".
The prosecutor said that despite Rarity telling one of the boys not to tell anyone he and the others did tell the police, but a prosecution did not result.
Mr Parfery said: "They persisted in this case in the hope that one day they may be heard, in the hope that one day they may be believed."
One of the men who testified against Rarity said: "I have come to court to do the right thing."
After the verdicts defence counsel David Taylor said that a background report would be required on first offender Rarity before sentencing.
Mr Taylor said Rarity suffered from a number of medical conditions, including sleep apnoea, and asked for his bail to be continued.
He said: "He takes a significant number of medications on a daily basis."
But the trial judge, Lord Fairley, told Rarity he had been found guilty of "three extremely serious charges".
The judge said his status had changed and he was now a convicted person "facing an almost inevitable jail sentence of a substantial length".
Rarity was remanded in custody ahead of sentencing hearing at the High Court in Lanark on August 10.