This question is asked a lot at GCSE level, and it can be approached in many different ways. You must think about the family vocabulary that you are familiar with. Think of words for family members, what they look like, what they like and whether you get along with them. This allows you to use other pronouns rather than 'ich...'. When talking about brothers, sisters, parents etc, try to think outside of the box and use comparisons, different tenses and connectives. Describing family members can be as basic or complex as you would like - it all depends on what you know and would like to say!
Start of by making a mind map with 'meine Familie' in the middle. From there, draw out different branches with different members of the family, and their characteristics and what they like (in German!). With this information, you can begin writing or sentences and drawing up comparisons between different family members and before you know it, you will have a full paragraph on your family written!