Lamine Yamal's father, Mounir Nasraou, said he considers his son missing out on the Ballon d'Or award as "the biggest moral damage done to a human being."
The Barcelona winger came second to Paris Saint-Germain forward Ousmane Dembélé in the Ballon d'Or voting.
"I think this is the biggest, I won't say theft, but moral damage done to a human being because I believe Lamine Yamal is the best player in the world by far, by a huge margin," Nasraou, who attended Monday's Ballon d'Or gala in Paris, told El Chiringuito TV after the event.
"It's not because he's my son but because he's the best player in the world. I believe there are no rivals. Lamine is Lamine Yamal. Something very strange has happened here. Next year there will be a Spanish Ballon d'Or winner."
Dembélé, 28, scored 35 goals in 53 appearances in all competitions for treble-winners PSG, who also won Ligue 1 and the Coupe de France in addition to their first ever Champions League trophy.
Barcelona president Joan Laporta said he believes the Champions League was the deciding factor in the Ballon d'Or race.
Yamal, 18, scored 18 goals in 55 games in all competitions last season as Barça won LaLiga, the Spanish Supercopa and the Copa del Rey, but lost in the Champions League semifinal to Inter Milan.
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"I think winning the Champions League has had its weight," Laporta said.
"We were hopeful. We had Raphinha, Lamine and Pedri nominated. In the end, Lamine and Dembélé were finalists. I'm sure he [Yamal] will achieve it. Time will tell but he's got great quality.
"I'm convinced this [finishing second] will only motivate Lamine more. He is a a winner. He has a healthy ambition."
The Spain international did make history on Monday by becoming the only multiple-time Kopa Trophy winner. Yamal also won the award, which recognises the best player under 21 years old, last year, shortly after helping Spain win the European Championship.
"Lamine's second Kopa is quite remarkable," Laporta said. "It's another recognition; no one has two Kopas."
Yamal, who signed a long-term contract in May with Barcelona until June 2031, knows what he has to do.
"I need to keep on working to win other awards in the future," he said on Monday.
Yamal's agent, Jorge Mendes, meanwhile, has no doubt Yamal has a great future ahead.
Asked after Monday's gala about his client finishing second in the voting, he said: "Lamine is going to win many Ballon d'Or awards."