Genetics do play a part in our physique, but we are not bound to them. Both of my parents are morbidly obese. They also have severe high blood pressure, heart problems, type II diabetes, high cholesterol, etc.
I've been working out since my teens and have a semi-clean diet (I'm very into gourmet cooking, so it's a challenge) and I am 13 lbs over my ideal BMI. Because of my efforts, though, my BP, sugar levels, and cholesterol are great.
We do tend to gain in the same areas as those in our family. The women in my dad's family tend to have heavy arms, as do I, and the women in my mom's family tend to have extremely hourglass figures, even when overweight. So, unless I wear clothing which is very waist-defining, I tend to look far heavier than I really am.
I think that people have the best success with healthy eating when they make gradual changes, it's easier to stick with it. Recognize that your genetics make things challenging, but it's important that we neither give up nor use them as an excuse.