Why does the narrator include the details about the old servants about the boron's sister and candide

In a castle of Westphalia, belonging to the Baron of Thunder-ten-Tronckh lived a youth, whom nature had endowed with the most gentle manners, His countenance was a true picture of his soul. He combined a true judgment with simplicity of spirit, which was the reason, I apprehend, of his being called Candide. The old servants of the family suspected him to have been the son of the Baron's sister, by a good, honest gentleman of the neighborhood, whom that young lady would never marry because he had been able to prove only seventy-one quarterings, the rest of his genealogical tree having been ost through the injuries of time.