Queen Elizabeth and her husband, the Duke of Edinburgh, have four children (Charles, Anne, Andrew and Edward) and eight grandchildren, as each of her children has two children of their own.
Charles, her eldest son and the heir to the throne, has two sons by his first wife, Diana: William (who should be the next king after him) and Henry (usually called Harry). Princess Anne has a son, Peter, and a daughter, Zara. Prince Andrew has two daughters, Beatrice and Eugenie, and Edward has a daughter, Louise, and a son, James.
The Queen is also a great-grandmother. Anne's son, Peter Phillips, and his wife Autumn, now have two daughters: Savannah, born in 2010 and Isla, born in 2012. Isla is 13th in line to the throne, although her parents don't really take any part in the royal family life (Peter Phillips works in sports sponsorship).