
The question arises whether the solution appeared on the first attempt. The alternative involves an initial multiplication of sisters before a second look at the sentence.
Riddles of this type offer entertainment. They also encourage patience. They encourage attention to detail. They encourage the satisfaction that follows when assumptions give way to clearer understanding.
The final answer stands at eleven people.
The group consists of the father, the nine sons, and the one sister. No additional siblings appear in the description. The wording itself contains the full information required.
The riddle invites sharing with friends or family members. Observation of responses can reveal how many encounter the common early calculation.