Bus driver Andrew Raybould died after suffering from severe pancreatitis, sepsis and multi-organ failure at Walsall Manor Hospital in February 2012.
His parents Geoff and Maureen from Aldridge said he had been discharged from the hospital three times previously without a diagnosis.
Walsall Healthcare NHS Trust accepted he should not have been discharged in the January and lessons have been learned following the death of Mr Raybould.
Medical negligence experts Irwin Mitchell represented the family and secured an undisclosed out-of-court settlement.
Mr Raybould first began suffering symptoms of abdominal pain, nausea, vomiting and constipation at the end of December 2011.
On January 3, 2012 his GP referred him to Walsall Manor Hospital for investigations as to the cause of his symptoms but was sent home.
By the end of January he had lost two stone in weight and was in constant severe pain. After being admitted to Walsall Manor again, he was eventually diagnosed with acute pancreatitis, acute renal failure and sepsis.
Mr Raybould was admitted to the intensive care unit on January 29, but he was too ill to undergo surgery and his major organs began shutting down. He died on February 2.
His mother Maureen, aged 59, from Aldridge, said: "This has been a devastating and traumatic time for us, but not as devastating as it was for Andrew, who was 21 weeks away from getting married and had a bright future ahead of him.
"We are grateful for the help from our legal team at Irwin Mitchell. With their help, we have finally found out the truth about Andrew's treatment at Walsall Manor Hospital."
Amir Khan, medical director at the trust, said: "We have offered our full and unreserved apologies for the failings identified in relation to the care Mr Raybould received which we accept fell below the trust's usual high standards.
"Our thorough investigation concluded that further investigations should have been undertaken and that Mr Raybould should not have been discharged on January 14, 2013.
"We also concluded that communication should have been made clearer for both the patient and his family around arrangements to return to hospital if he continued to feel unwell. We accept that communication could also have been improved with Mr Raybould's family as his condition deteriorated."