Following up from ‘how many people’, you can simply add who they are

おとうさん と おかあさん と わたし です。

Put と in between different family member to indicate ‘and’

When asking a question about specific family member

いもうと が いますか。 Do you have a younger sister?

おにいさん が います。I have an older brother.

Your task is to create your own family tree using PowerPoint introducing each family member