A Sydney father intended to die alongside his wife and two children when he unleashed a lethal gas that killed them as they slept, a NSW coroner has found.
Fernando Manrique, 44, and his wife Maria Lutz, 43, were about to divorce when they were found dead from carbon monoxide poisoning along with their children Elisa, 11, and Martin, 10, and the family dog, Tequila, in their northern Sydney home in October 2016.
The inquest had previously been told Manrique was in financial strife and having an affair with a teenager in the Philippines when he killed himself and his family.
He owed at least $15,000 to the tax office, had $28,000 in credit card debts and was struggling to pay off the family's two mortgages totaling more than $500,000.
Despite his debts, Mr Manrique was also supporting a woman he was in a "serious relationship" with in the Philippines, where he travelled for work each month.
The woman, known only as Jamilyn, was 17 when she met Mr Manrique in 2015 at a bar where she worked.
Deputy state coroner Elaine Truscott on Friday ruled Manrique's death a suicide and emphasised he had acted alone in killing his family.
"The evidence establishes that it was just after Maria had told Fernando that the marriage was over and he had to find somewhere else to live that he put into action his plan to take their lives," she said.
"Their lives were stolen by someone who should have been their protector and provider."

Parents of school children view inscriptions on a memorial bench during a memorial service for the Manrique-Lutz family at St Lucy's School in Wahroonga. Source: AAP
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