Two youths have been sentenced to more than six years detention for their part in an attack which left a man dead.
Alexander Pullar's wife died in January last year
Alexander Pullar, 63, was battered to death in March - a year after his diabetic wife Moira was given a fatal dose of insulin in hospital.
The couple's son Alex said the sentence imposed on Christopher Slonaker, 17, and a 15-year-old, who cannot be named for legal reasons, was too lenient.
Another 15-year-old, found responsible for the death, will be sentenced later.
During an earlier hearing, the third teenager was held to be unfit to plead because of insanity.
The judge in his case, Lady Paton, heard examination of the facts at the High Court in Glasgow and concluded that he had murdered Mr Pullar.
He is currently in a mental hospital and is expected to appear in court later this month.
The other two youths were originally charged with murder, but last month their guilty pleas to charges of assault and robbery were accepted.
Their 15-year-old friend went on to kick and stamp on Mr Pullar's head with such ferocity that his face was unrecognisable. He died in hospital the next day.
Mr Pullar was found seriously injured in a pub car park
Slonaker was detained for three years and four months after admitting taking part in the initial assault on Mr Pullar by hitting him with a guitar fret and taking money from his pockets.
The other 15-year-old, who admitted punching Mr Pullar and rifling his pockets, was sentenced to three years.
Lord Philip said the youths were "out of control" and told them: "The despicable and unacceptable nature of your crime has to be acknowledged and the public protected."
He described Mr Pullar as a "frail, vulnerable and defenceless man" who they youths knew would be unable to defend himself.
Outside the court, Alex Pullar, 41, said the two accused should have got seven years each.
"I knew it was going to be too lenient when I came here today - their age should have made no difference," he said.
"We just want to get this tragedy out of our lives and put it behind us."
Sentence was passed the day after a sheriff delivered his findings following a fatal accident inquiry into Mrs Pullar's death in January last year.
Sheriff Robert Dickson said the 62-year-old had died after poor handwriting on her hospital records led to her being given 10 times too much insulin.
Airdrie Sheriff Court heard that the nurse at Monklands General Hospital who gave the wrong dose failed to have it checked or consult a doctor.