My sister says she has ringworm on the scalp. are family members more likely to get the same thing?

Sometimes: Ringworm is actually a fungal infection (not a worm) of the skin. You can treat it with over the counter antifungals such as Clotrimazole cream (and there are many others). It is transmitted by contact between family members and close acquaintances. If it persists longer than about 2 weeks, you might want to see a dermatologist for alternative applications.