Answer:
This is quite impossible to say, since art historians know next to nothing about Hubert van Eyck. He seems to have existed, he may be buried in the Ghent cathedral. There was even a plaque saying he painted the Ghent altarpiece "which was finished by Jan". Most historians disbelieve this, since there are no different styles in this large work. One or two works are ascribed to Hubert, by some, whereas others deny this.