Immunodeficiency disorders are disorders that interfere with the body’s ability to protect itself against infection. The body defends itself by producing substances called immunoglobulins. Hyper-IgM syndrome is a primary immunodeficiency disorder involving normal or high levels of immunoglobulin M (IgM) and decreased levels or absence of other immunoglobulins, making patients prone to bacterial infections. Most cases are linked to a mutation in a gene on the X (sex) chromosome. Which of the following groups is most likely to have this condition?