When you hire a new brother, he will randomly have a series of stars next to some of his Attributes:
These denote the brother's talents. Talents allow a character to progress better than others in a certain stat. These talents are completely randomly assigned, without any connection to a background or trait.
A talent increases the additional attribute points available upon level-up. 1 star increases the minimum by 1, 2 stars by 2 and 3 stars also increase the maximum by one.
Willsama974 wrote a nice table that shows this very well:
|Regular||One Star||Two Stars||Three Stars|