Older brother Frank Hardy is darkhaired; his brother Joe is blond. Their father, Fenton Hardy, has an international reputation as a master detective, but has decided to set up his office in rural Bayport. He and his sons collaborate on some cases, and he occasionally makes deductions which would do credit to Sherlock Holmes. Their mother, Laura Hardy, rarely enters the plot; her role is purely domestic.

The Hardy boys' chums are all cleancut. Chet Morton is a chubby young man whose dominant trait is a constant desire to eat. Biff Hooper is a muscular athlete who is good with his fists.

Another close friend is Tony Prito, who was included, McFarlane has suggested, so that ethnic minorities would not feel neglected. Chefs sister, lola Morton, is Joe's steady girlfriend, and Callie Shaw is Frank's. Stratemeyer established a rule that these relationships should "not...