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.
Valves in Veins (Venous Valves) - One way valves in the veins prevent backflow (due to low blood pressure) - Skeletal muscles surrounding the veins squeeze them which pushed the blood up towards the heart. - Standing still for a long time causes fainting.