[pvaldes]

Some brothers can have different mothers or fathers.

As the origins of Colon were unknown his real family relationships were also unknown. He toke a lot of measures to hide their identity including lying about it. The scientists did DNA tests to Italians with surname Colomb and discovered an unexpected amount of variability (Those people weren't related).

It seems that Colomb (Pigeon?) was a surname applied on Italy for children without parents, so was shared by different people without a real genetic relationship. John "Snow" style. This means also that it was also the perfect surname that somebody wanting to hide their past would chose. This way he could just pretend that didn't knew about his family when interrogated by Kings and powerful people. Refusing to answer otherwise would be extremely dangerous.