The mother of the preteen boy filed a civil suit on her son's behalf in October, naming the mentor and the organization’s local chapter as defendants.
The woman, her son, and the man who assaulted him cannot be named because of a court-ordered publication ban.
The lawsuit is seeking damages for the boy’s mental and emotional distress and anxiety.
Big Brothers Big Sisters of Eastern Newfoundland filed a statement of defence on Dec. 13.
Those court filings state that there is no connection between the volunteer's sexual assaults on the boy and his role with Big Brothers.
The statement claims that these were "deliberate, criminal acts" by the man, which are not at all tied to the organization.
Mentor got 2 years in prison
The former Big Brother was sentenced to two years in prison in November after pleading guilty to three sex-related charges involving two preteen boys, including two counts of touching for a sexual purpose, and one of invitation to sexual touching of a person under the age of 16.
The man was also placed on probation for three years, and his name will be listed on the sex offender registry for 20 years.
He assaulted the first boy, his Little Brother, for a period of three years. The second victim was a family friend, who was staying at the boy's house one night in the summer of 2013.
The man also has a prior conviction from 2006 for fraud under $5,000. But fraud is not on the list of crimes that can bar someone from becoming a Big Brother volunteer.
The civil suit accuses Big Brothers of negligence in the screening and selection process.
But in the statement of defence, the organization "denies each and every allegation set forth in the statement of claim."
It also denies that Big Brothers was negligent.
The court documents contend that the sexual assaults on the boy are criminal acts that are "entirely outside the scope of [Big Brothers]," and the assaults "were not related to the scope of authority or duty or position assigned to [the man] as a Big Brother."
The filings also defend Big Brothers' screening practices in relation to the mentor, stating they followed the organization's national standards.
Those include extensive interviews with trained staff, a criminal records check, vulnerable sector screening, three to five references, and an assessment of the volunteer by a trained social worker.
Bruce MacDonald, president and chief executive of Big Brothers Big Sisters of Canada, told CBC News he would not comment on anything relating to the ongoing legal proceedings.
But he indicated by email that a review of the organization’s national standards is continuing, specifically as it relates to vulnerable sector checks and the permission forms currently used by the group to see if they allow for personal information to be shared.