Leah Croucher's family were hit by a second tragedy following her disappearance after her brother killed himself feeling "hopeless" and "lost".
Haydon, 24, took his own life after telling a therapist her was struggling to cope with his sister's disappearance.
After explaining how he had become fixated on killing himself, Haydon was found dead in his flat in Bletchley, nine months after Leah vanished.
He was discovered by his mum Tracey Furness and sister, Jade, before he tragically later died in hospital.
Leah went missing in February 2019 after last being seen on CCTV in Buzzacott Lane, Furzton, Milton Keynes, just after 8.15am, walking in the direction of Loxbeare Drive and Chaffron Way.
Now, human remains have been found in the search for Leah, with Thames Valley Police going on to launch a murder investigation earlier after a rucksack and other belongings of Leah's were discovered during forensic examinations in Loxbeare Drive.
The forensic examination continues and will do "for a significant period of time", and it is likely to take some time to formally identify the deceased, the force said.
During Haydon's inquest in 2020, assistant therapist, Chantelle Tillison said in the last of three sessions he felt there was no future for himself.
Ms Tillison said: "He felt hopeless and said he would be better off dead.
"He explained Leah was still missing and found it difficult to cope with no family support.
"He fixated on hanging himself. He said if he had the means to hang himself he would."
Following his death, mum Tracey said Haydon was "consumed with pain and anguish" and took his own life shortly before the nine-month anniversary of Leah's disappearance.
She said: "What I am going to say will not be easy to hear. Some will feel outraged at the level of openness I am going to share.
"We cannot any longer hide from the reality, we cannot pretend this doesn’t happen we can not bury our heads in the sand and shy away from the horror of ill mental health.
"I cannot pretty this up, I wish I could.
"On Thursday 14th of November, my son felt so alone, so lost, so broken that he felt he had no other choice other than to take his own life.
"Haydon was so consumed with pain and anguish and despite the love around him it wasn’t enough. His mother's love and that of his entire family was not enough."
Jade wrote: "Haydon, me mum and dad held onto your hand until the very last moment but we will hold you in our hearts forever! You will always be with us until the day we meet you again.
"Mum and Dad might not be together but one thing that will never waver is the love they have for you their darling son!
"We will all stick together as a unit and get through the pain with the love and support of both of our amazing stepparents Dave and Claire."
Samaritans (116 123) operates a 24-hour service available every day of the year. If you prefer to write down how you’re feeling, or if you’re worried about being overheard on the phone, you can email Samaritans at jo@samaritans.org.
Childline (0800 1111) runs a helpline for children and young people in the UK. Calls are free and the number won’t show up on your phone bill.
