There isn’t a typical age for the formation of spider veins. As they are linked to hormonal changes, that means any time your body has hormone fluctuations, spider veins can follow. For women, that can be as early as your teenage years, and surely during pregnancy. Of course, menopause is a prime time, but most women have at least a few spider veins before its onset. Also, weight gain and spider veins go hand in hand, so even younger women who gain lots of weight can see spider veins develop.
It’s easy for younger people to think of spider veins showing up on aging legs. It is true that aging increases their appearance. This is probably due to two factors: weakening support tissues and veins in the legs, and thinning skin. Thinning skin may allow formerly unseen clusters to start to show themselves as we pass our 50th birthday.