Internet New Zealand chief executive Vikram Kumar believes a child is one of those served with a copyright infringement notice under the three strikes rule in anti-piracy legislation.
The three Telecom customers will be a test case for the legislation brought in a year ago, and they could face a fine of up to $15,000.
The infringement notices have all been filed by the recording industry.
Mr Kumar said he understands some 3000 people have received infringement notices.
In three of theTelecom cases, he said a child and a guest whose used someone else's computer may be involved, with the liability resting with the person who holds the account.