Grandparents have always been important. Today, they're even more important. In busy, two-career and single-parent families, an involved grandparent goes a long way to filling a void for children. In extreme situations, the courts have found it's often a grandparent who can reach a troubled teen when no one else can.
Some people, genetically, are born with weaker or smaller veins than others - and some people are born with larger, and more flexible vein tissues. Due to genetics, some people just have poor, weak veins. This only affects the large return veins you can see however - the veins which transport the rest of your blood are likely fine. Regardless of the vein size, blood can still be drawn. I personally have smaller and weaker veins, and can still donate, but sometimes it takes a few tries.
Simply the heart, a big muscle, is connected to a series of tubes, the arteries and the veins, which carry blood to the various parts of the body. Arteries carry the blood away from the heart, while veins bring blood back to the heart. The arteries are connected to the veins via very small vessels called capillaries. Electrical and chemical signals to the heart cause it to pump the blood into the arteries. Further, a number factors can cause the blood vessels to expand (dilate) or contract. In doing so they can increase or decrease the amount of effort the heart needs to put forth to deliver the blood.