A child is a child regardless of noble status. And as they mentioned in the LN, the closest advisers young nobles have and the most contact they have is not their parents but their aides. This is why they choose the aides for their children very carefully because they will be the most trusted people of their noble kids. Also, the aides are very cunning - see this IRL, too - and are good in planting seeds little by little as they are playing the long game.
In ASOIAF/Game of Thrones, this was front and center, and the nobles were adults. Imagine how much easier it is for aides to manipulate children.
Wilfred is just stupid.! Im glad he got disowned being a Lord…