Is it permissible for the questioner's sister by suckling, who was nursed by the questioner's mother more than five times, to uncover in front of the questioner's maternal uncle and her paternal half-brothers, given that the questioner was nursed by the mother of her sister by suckling an unknown number of times?

This girl is your sister through rada'a (nursing), because she suckled from your mother five times or more. Therefore, your mother is her mother through rada'a, and your father is her father through rada'a.

Based on this, your maternal uncle (your mother's brother) is her maternal uncle through rada'a, and it is permissible for her to uncover in front of him. Your brothers from your father are also her brothers, because the milk of rada'a was due to your father, so he is considered her father through rada'a, and all his children are her brothers.