Missing brother Leah Croucher, 20, died suddenly.
Haydon Croucher's broken-hearted father, John Croucher today confirmed the death of his son, nine months after his daughter disappeared without a trace.
He wrote on Facebook: "We love and miss you very much. Our world cannot be more ruined than now."
The 24-year-old was involved in the search for his younger sister, who had been 20 years since missing at Milton Keynes this February in a case that puzzled detectives.
In his heartbreaking post on social media tonight, Haydon's father, John wrote: "Haydon is a kind, generous, funny, intelligent and loving person and in his words a very handsome man. He has a big heart. He has leaving two family and friends who love him so much. We will all miss him. Always "
Leah disappeared from her home in Quantock Crescent, Emerson Valley on February 15.
He did not tell his parents where he was for 75 minutes on Valentine's night.
Since then they said in an interview with tears that they believed their daughter had been killed.
He was last seen on Buzzacott Lane in Furzton, Milton Keynes right after 8.15 am and walked to work towards Loxbeare Drive and Chaffron Way.
Leah disappeared the next day on her way to work at Milton Keynes.
His cellphone and bank account have not been used since then.
Three witnesses reported that a young woman who might have been Leah was seen by Furzton Lake, another lake in the city on February 15, between 9.30am and 11:15am.
He was reported as "angry, upset and crying". Lake search was carried out but nothing was found.
John Croucher wrote tonight: "What kind of life can you talk to your son on Thursday night to convince him that we all feel the same sadness on Friday the 15th, approaching nine months without news about Leah is a terrible thing to deal with.
"We promised to meet the next day so we could face it together. Hours later the police knocked on the door and told you that Haydon was fighting for his life.
"Doctors say the prognosis is bad. You sit by his bedside and see it getting worse every time. You have to say goodbye. What do you say in that situation?
"You told him you loved him. You remember funny times. You begged him to come back to us. Finally you must tell him to go and make peace. You hold him when he slips away. To say our hearts and minds are broken is an understatement statement. .
"Haydon is a kind, generous, funny, funny and loving person and in his words a very handsome man. He has a big heart. He is only 24 years old. Too young to leave forever. He has left two families and friends who love him so much We will all miss him Always
"Peace, Haydon. If Leah were there with you guarding each other as usual, until we got there. We love you very much and miss you both. Our world cannot be more ruined than now."
The Croucher family has another daughter, Jade Croucher, who is the eldest of three siblings, and who posted a series of broken heart emojis on her Facebook page tonight, along with loving family photos with Haydon and Leah.
The brothers have searched for their missing sister completely.
In May, Haydon appeared in the Aylesbury crown court on charges of threatening a man who was dating Leah.
He received a restraining order from Judge Francis Sheridan and the prosecution was canceled.
At that moment the judge told him, "This is truly a tragedy. You and your family are entitled and entitled to our sympathies."
The judge continued: "I cannot go into the details of the police investigation but can tell you it is being controlled at a very high level. This is detailed and, if I say it respectfully, they really try hard.
"You must allow them, however strong you feel, to carry out an investigation. You will jeopardize their investigation if you put it in your head that someone is responsible for it.
"The police have fully investigated the person you suspect. At this stage, no one supports the suspicion.
"May I beg you to behave so that the police can complete this investigation, I want to say 'with a happy ending,' but I don't know. He is missing."
Apart from an emotional request from the Crouchers, as well as a £ 5,000 gift offered for any information that could have caused him to be found, police have not found any trace of him since he disappeared on 15 February.
Her parents earlier this year revealed in a heartbreaking interview they believed their daughter had been killed.
In an interview with tears this morning last month, Leah's parents, Claire and John said they did not believe she had disappeared on purpose.
Claire said: "If the worst has happened, I want my daughter's body back so that her family can be buried and we can say goodbye – because everyone deserves it."
John added: "To be honest, I don't believe he ran away. He has gotten enough money in the bank and it hasn't been touched. If you run away, surely you will take something?"
His mother also spoke publicly for the first time about her daughter's relationship with an older man – a 27-year-old brother of Leah's protective brother Haydon, accusing him of "caring for" him, before a restraining order was served.
Claire said on the program: "We did not know the relationship before he disappeared. We have known since he saw someone but that person has been spoken to."
Police had previously confirmed that there was no reason to suspect the man.