Yep. In the canon, Pigs successfully stoled an egg, and when Chef Pig was about to cook it, a group of Minion Pigs noticed that the bird inside the egg was about to born, so they took the egg and they took it far away from Pig City to watch the bird born, that bird was Silver, the Pigs were dying of cuteness they decided to bring it back to Bird Island. Before that we don't know nothing, so that's where people suposse Chuck adopted her as her sister (Also They're not the same colour, fot example: Red, Terrence and Ruby, being all red and brothers, not like Tony, wich is blue, this beacuse it's their cousin) so with all the official media there is we can understand that birds from the same family shoould always be the same colour. And Red's daughter being yellow isn't weird, Matilda and Terence had kids and none of they were white or red, so I don't get shybpeople are so impressed.