Genes are passed on from generation to generation. When a male and a female produce an offspring, the offspring would get half of their genes from their mother, and the other half from their father.So your parents get half of their genes from their parents, (which in this case, are your grandparents) and they pass them on to you. Unlike your parents, you get traits from both sides of your family, some from your mother's side and some from your father's side.
This is why you share similar traits as your grandparents and at the same time,there is also a chance that you also share some (of course not all) traits with your direct cousins, because they also share some traits to your grandparents.
