Bellingham's younger sibling, Jobe, scored a brace for Sunderland in a Championship match against Rotherham in August 2023, sealing a 2-1 victory for his side, while his elder brother and Ancelotti watched on from a distance.
However, Jude's delight soon gave way to horror after Madrid boss Ancelotti told him he intended to recruit Jobe and play him in his usual midfield position.
Speaking on the first episode of his 'Out of the Floodlights' documentary series, Bellingham told viewers: 'I'm in shock that he's scored twice and then I'll never forget as we're coming out Ancelotti goes to me, "F***ing hell, we brought the wrong one."
'And I'm like, "You're joking." He says, "No seriously, I'm going to bring him in." I said, "Well where are you going to play him?" He says, "In your position."
Jude Bellingham revealed Carlo Ancelotti cracked a brutal joke over his brother, Jobe
'I was like, "F*ck that!" And then finally he gave me a little smirk and my heart just dropped and I thought okay, fine. And then I'm like, no pressure for today!'
Later that day, though, Bellingham reminded Ancelotti exactly why he had scrambled to snap him up after scoring a brace of his own against Almeria.
One of England's heroes at Euro 2024 during the summer, Bellingham sealed his sensational move to Madrid in a £113million deal from Bundesliga side Borussia Dortmund.
He was handed the No 5 jersey, once infamously sported by the legendary Zinedine Zidane at the Bernabeu.
The moment he was first shown his new shirt was also captured for the YouTube video, leaving the 21-year-old humbled.
'I will never forget that moment seeing my name with the No 5 on it,' he said.
Bellingham then added: 'I'm not coming here to be Zidane, he was amazing. I'm trying to be Jude Bellingham who continues the No 5 legacy.'
Last season, the red-hot Bellingham scored a remarkable 23 goals from 42 appearances across all competitions, including a tally of 19 in LaLiga alone.
He has endured a more sluggish start to the current campaign after suffering a muscle issue in training last month. Bellingham could return against Real Sociedad this weekend, however, after returning to sessions this week.