Jeffrey Cain, two weeks away from getting married, couldn't keep his hands off his fiancee's 10-year-old sister.

Three times - starting when she was nine - he slid a hand into her underwear to feel her genitals.

On Monday, Cain, 24, was sentenced on a joint recommendation to eight months in jail and two years of probation after pleading guilty to sexual interference.

"I lost a spouse that day and a best friend," his ex-fiancee wrote in a victim impact statement filed earlier. "I have terrible nightmares of Jeff Cain sexual(ly) abusing my sister and laughing at me while he does the unforgiven, devilish act."

The victim herself filed a drawing of Cain as "King of the Bad Germs." "Mr. Sick," she wrote. "You know it would come to this. I hope you didn't think you could get away with what you know you did." "I hate u Jeff Kain (sic)."

The first assault took place in March 2009. Sleeping over at Cain's fiancee's house, the girl awoke to Cain touching her. She feigned sleep and told no one.

Around June 17, 2010, she was watching a movie with Cain on a basement couch as their friends and relations planned his upcoming nuptials upstairs. Two friends popped downstairs to say goodbye, and found them huddled under a blanket.

He'd touched her again.

But it was not until she saw a sexual education video about uncomfortable feelings and bad touching that the truth emerged.

The girl had merely been telling her mother about school over the phone. A victim of abuse herself, her mother asked the girl if she had ever had those bad feelings. Yes, the girl replied, promising she'd tell her mother all about it when they saw each other next.

The family, tearful throughout the sentencing, remains wracked with guilt.

"I blame myself for what Jeff has done," the ex-fiancee wrote in her statement. "I always told my siblings my house was to be the safe/fun house... But really it was a house of pain and torture."

"I know that my words will not take away that guilt," Judge Lise Maisonneuve said. "It is absolutely not (their) fault."

"I think there's a lot of healing to be done by hearing you admit wrong," she said to Cain, who apologized to the family for ruining what could have been a "perfect, perfect life."

Maisonneuve asked the diagnosed pedophile - who is considered a low to moderate risk to reoffend - be sent to a treatment centre.