When you replace a noun with a pronoun, ask yourself: Does the noun show that there is one person or many people? Does the noun show whether the person is male or female? Then, choose a pronoun that also gives that information. This is called “concord”, or agreement between the noun and the pronoun. For example:

My family went on holiday in December. We went to Knysna. (many people)

My father swam in the sea every day. He even swam in the rain. (one person, male)

My sister went running on the beach. She got very fit. (one person, female)