The patient has hemophilia A, characterized by a von Willebrand deficiency. It is an X-linked recessive disorder diagnosed in primarily male infants. The patient should undergo genetic testing to verify the diagnosis. Because de novo mutations can occur, parents should undergo genetic testing to determine if the parents are carriers; this affects future childbearing decisions. Due to the severe nature of the infant’s deficiency, it is unlikely the 12-year-old male sibling has the disease but has been undiagnosed (most diagnoses occur in infancy, especially in male children). The 3-year-old female sibling is unlikely to have the disorder because it is X-linked recessive. There are ethical issues around testing the female sibling to determine carrier status; she can make the decision to be tested as a carrier when she is of childbearing age.