After a coroner's report yesterday ruled the actions of the older of the brothers was "the most significant factor" in Stephen's death, his family revealed that they would ask the Solicitor-General to review the case.
They hope to have a new manslaughter charge laid against the teenager.
The Dudleys believe that the coroner's report shows clearly that at least one of the teenagers could - and should be - held accountable for Stephen's death.
"The Dudley family will be asking the Solicitor-General to review this case in light of the coroner's findings with the aim of laying a manslaughter charge," said the family's lawyer Nikki Pender.
Although double jeopardy rules exist in the New Zealand legal system, the fact no one had been tried for manslaughter meant a new charge should be able to be laid.
Retired District Court Judge Roy Wade said the Dudley's wish should not be too hard to grant.
"Provided the manslaughter charge was withdrawn and not dismissed, the Crown should be able to re-lay it without too much difficulty," he said.
"There is no time limit involved.
"A potential problem might be if a deal was struck between the Crown and defence such as the youths pleading guilty to a lesser offence in exchange for the Crown withdrawing the manslaughter charge."
AUT law professor Warren Brookbanks said the coroner's findings "did not bind the police to a further investigation", which may result in new charges.
"It is a matter of prosecutorial discretion," he said.
"Also the law is clear that the fact that a charge has been withdrawn is not a bar to other proceedings in the same matter.
"In deciding whether to lay a fresh charge the prosecuting authorities would be guided by the test for prosecution - that is whether the available evidence is sufficient to provide a reasonable prospect of conviction and whether the prosecution is required in the public interest.
"If those tests are met there is no reason in principle why a fresh prosecution for manslaughter should not be brought, although such a procedure would be rare."