Boots is the second oldest cat in the Kat Family, introduced in The Sims: Unleashed along with its owner, Ginia Kat. In The Sims: Superstar, when a Sim reads the tabloid, one of the news features is about a (random) star saving Boots, a local favorite, from a tree. Boots is a Siamese cat. The name may be a reference to the "Puss in Boots" fairy tale of the same name, and perhaps refers to the dark fur around Boots' paws that slightly resembles "boots."
Although the pronouns in the bio imply Boots is male, using the A Friend Indeed spell on Boots reveals that they are female.