Think of what you want to write about your family. You can tell their name, age, their characteristics, etc. You can start like this...
"Family is a source of love and the best supporters on earth. Everyone has a family whether its a single mom, or a dad or just grandparents. Like everyone, I have a family that makes me happy." ....and then you can start telling story about your family. Includes your happy moments with them to make it longer and more interesting.