I would recommend once you can tell the males from females to not to hold the roos as much, until they are a couple months old. I hold them a lot the first few weeks, then only if they come up seeking attention. I've found forcing attention on a cocky little cocks is good way to make them aggressive. If they reach maturity without acting aggressive I've never had one start later in life. If they act aggressive though when younger it does tend to get worse. (This is not really specific to D'uccles - just general roo advice - D'uccle roos tend to be pretty nice, but I had one mean one, that I'm convinced got that way because we would force cuddle him all the time as a baby when he had not interest in it.)
Mine do this a LOT! But i do think you are right about the forcing attention thing. I've done both, and the ones i forced never really did get the same level of friendliness anyway. And i do think they did be more liable to get aggressive.
