Jack Doyle, who would have called Elaine "aunty", was stabbed through the heart during a party in Greenock's Antigua Street in January 2012.
His father, Elaine's brother John, commemorates both lives in tattoos on either side of his neck.
John Doyle, 49, has been watching the trial from the public benches at the High Court in Edinburgh.
An earlier trial saw teenager Steven McIntyre convicted of murdering 17-year-old Jack Doyle when a jury rejected his claim that he had been acting in self defence.
Judge Sean Murphy QC told McIntyre, then 19, that he must serve at least 15 years of a life sentence before he could ask the parole board to free him.
The trial which has just concluded at the High Court in Edinburgh has been a major success for a specialist unit set up by the Crown Office in June 2011 to help local police and prosecutors crack what are often called "cold cases".
Describing the work of the new unit, advocate depute Frank Mulholland QC said that 93 unsolved murders dating back to 1974 would now come under scrutiny.
There are believed to be some 700 suspicious deaths added to the files of Scottish police forces since 1940 which remain unresolved.