The pair, who are ambassadors for Dementia Australia, reportedly broke down onstage as they spoke about their mother's condition during a Q&A session for Dementia Australia at the Convention Centre in Brisbane.
The duo appeared at the event to raise awareness for Dementia Awareness Month, a cause close their heart since their mother was diagnosed with Lewy Body dementia and progressive supranuclear palsy earlier this year.
"After several years of misdiagnosis, our mum Coleen has finally (been) given a diagnosis of Lewy Body Dementia with progressive supranuclear palsy," the Australian music artists said in a statement to the Courier Mail.
"It has been an incredibly heartbreaking and frustrating time trying to find a definitive diagnosis. We have had incredible support from friends and family," they added.
In June, Jess and Lisa shared a powerful message on Instagram vowing to break down the stigma associated with the disease.
"We are here to break the stigmas surrounding neurological disease, and EMPOWER those living with dementia, campaigning for ongoing medical research and a more compassionate, inclusive Australia," they said.
"Thank you to all the politicians and media who showed up today and are helping to make Australia a more empathic and supportive community for those living with dementia."