One person that Holden obviously likes is his brother, Allie. Allie died before the content of the novel takes place. In the beginning of the novel, Holden rhapsodizes about how Allie was one of the best people in the world. His poetry clad baseball glove is Holden's prized possession.
A second person that Holden likes is his sister Phoebe. The significance of these two likings is that Holden seems to like younger, innocent people. He doesn't much care for adults.