How old was Dora the explorer's twins?

Dora the Explorer's twins, Diego and Alicia, are introduced in the spin-off series "Dora and Friends: Into the City!" They are depicted as toddlers, roughly around 2-3 years old. However, in the original series, Dora herself is about 7 years old, and the twins are younger than her. The series focuses on Dora's adventures rather than the specific ages of the twins.