Are "big" and "little" the usual words used to refer to the age of a person. If I am 52 and my mother is 85, for instance, do I say she is "bigger" than I? Is there a different word used for objects, e.g. an old book or an old house?
For people बड़ा and छोटा are fine, although there are also बूढ़ा and जवान if you really want to specify that you are referring to age. For objects you would instead use पुराना and नया.