Dean Lucas and Adam Coleman, both 33, were living in Edmonton, Canada and had driven down to Mexico for a surfing trip.
Their families say they will be going to Mexico amid media reports that two unidentified bodies were found inside a burnt-out van resembling theirs.
A family statement said they hold "deep fears" but police did not comment.
"Dean and Adam were travelling in a van, departing from Topolobampo on Friday 20 November to Guadalajara but did not arrive on their scheduled date," a joint statement said.
"The families hold deep fears for the safety of their sons but stress that they are still waiting for details to be confirmed."
Australia's Department of Foreign Affairs has confirmed it is providing consular assistance to the families.
Dean Lucas' girlfriend, Josie Cox, posted a message to Facebook saying she was devastated after learning how he was going to propose.
"I definitely don't doubt that there's something that's happened, something that we should be worried about," she told the media.
Fears are growing for two Australian surfers travelling through Mexico who have been missing since 20 November.