The 28-year-old Australian star and her 21-year-old sister Annabelle were both taken to hospital in critical conditions after the crash in New South Wales.
While Pia wrote "Thinking of you, ' on Instagram as news of the crash broke, Heywood urged his fans to keep Jessica to send 'love support and prayers" to both Jessica and her 21-year-old sister Annabelle.
According to local news, the two sisters were airlifted to separate hospitals and have since been joined by family, where they remain in a critical condition.
Their mum and dad, Vivian and Lars Falkholt, 60 and 69, respectively, were killed in the head-on collision at approximately 10.45am on Tuesday morning.
Witnesses and police pulled the two women from the wreckage as the vehicles were engulfed in flames.
The Daily Telegraph report that a vehicle driving on the wrong side of the road caused the collision, hitting the Falkholt family head on as they made their way home to Sydney following a short festive break.
Police have reportedly said that one of the cars was travelling on the wrong side of the road.
Family members are by their side in hospital.
"This Christmas and New Year period is meant to be a time of happiness and to spend time with family and sadly for many, this has resulted in tragedy", he continued.
Actress Jessica Falkholt played Hope Morrison in Home and Away.
Police said they were "investigating the behaviour" of the driver of the other auto just prior to the accident after talking to witnesses.