A second letter was discovered inside the home of a family found dead in a suspected double murder-suicide in Perth.

The bodies of Leon, 16, and Otis, 14, were found at the family’s Mosman Park home on Friday after a person known to the family became concerned for their welfare.

Their parents, mother Mai, 49, and father Jarrod Clune, 50, were also found in different parts of the property, along with a note, police said.

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Leo, 16, and Otis, 14, were found at the family’s Mosman Park home (Nine)

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It was a carer, arriving at the home on Friday morning for an appointment, who found a note on the door warning them not to enter and instead call the police.

A second note was later found inside the home which revealed more details, including instructions on where they wanted their finances to go.

Friends of the family have revealed the children’s National Disability Insurance Scheme (NDIS) funding had been recently cut.

Both boys lived with severe autism, one was non-verbal, and friends claim the couple were at breaking point.

The couple cared for their children full-time, with limited support.

Their parents, mother Mai, 49, and father Jarrod Clune, 50, were also found in different parts of the property. (Nine)

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Friends say they were desperate for help.

“The very people the NDIS was created for are the very ones who can’t get the services they so desperately need,” the friends said in a statement.

“The constant battle for services to help with their very high support needs boys was exhausting, never-ending and filled with rejection.”

“When the family looked for help, they were always rejected and told their boys were too difficult.”

9News understands it was a joint decision by both parents.

Police are still investigating the circumstances of the family’s deaths.

Two parents and two children have been found dead in a Perth home.Friends say the couple’s NDIS funding had been cut. (9News Perth)

Disability advocates are now calling for greater support for families with disabilities.

“A huge number of people who have had NDIS funds cut, especially over the last six months,” disability advocate Samantha Connor told 9News.

“I’d love to see more peer support, I’d like to see the brakes put on for the changes to the NDIS at the moment.”

Premier Roger Cook described the deaths as a “double tragedy”.

“That the lives of two innocent children have been taken is heartbreaking,” he said.

Readers seeking support can contact Lifeline on 13 11 14, or beyond blue on 1300 22 4636.

National Sexual Assault, Domestic Family Violence Counselling Service 1800RESPECT (1800 737 732).