Nobles can be born with or acquire Traits. These are visible on their profile page and can be both positive or negative. Traits on Noble Babies can be seen after you choose their role.

A trait can last a lifetime or only a few minutes and can modify the Noble's stats, abilities, can restrict them to the Keep, or open up new actions for others interacting with them. Short-lived traits can be removed using gold.

Some of the potentially affected statistics are:

The number of traits depends on a Noble's quality, the number of traits their parents have and some luck. Before maturing a Noble baby, most of their traits can be rerolled (if not inherited). The number of rerolls depends on a Noble baby's quality. The higher the quality, the more free rerolls available for that baby. If you run out of free trait rerolls and you still haven't rolled a trait you'd like to keep, you can keep rerolling using gold, but the cost increases with every roll.

Keep in mind that traits inherited by the parents cannot be rerolled.