What gives people hemophilia?

Depends: There are two types of hemophilia (besides the a, b, c) - genetic (the most common and well-known) and acquired. Genetic is just that - it's from birth due to a genetic mutation. The acquired form develops later in life and is often caused by an immune reaction from an infection or substance (like a medication) that causes the immune system to attack certain parts of the hematologic system.