Answer: Santosh's mother already had five sons. So they no longer had a wish for a son. That's why, her grandmother asked the holy man for the blessings of a daughter.
Explanation: The holy man who blessed Santosh's mother was surprised because Santosh's grandmother said that they did not want a son. As she already had five sons, they only wanted to be blessed with a gifted child. The holy man was surprised because every mother wanted to give birth to a son, contrary to Santosh's mother.