While your genetic makeup is an important factor, only about 15% of weight problems can be attributed to your family tree. Part of this is related to how efficient we are at storing calories.
If you store your fat in your abdomen, you are considered an "apple" shape. If you carry fat mainly in your hips, thighs and buttocks, you are considered a "pear" shape. Before the apple/pear terminology, body types were classified by the controversial concept of "ectomorph" ("naturally" thin) vs. the "endomorph" (more muscle and fat). Most people were considered "mesomorphs", which are in the middle.