Is it permissible for the milk-brother's father (the sister's husband) to see his wife unveiled?

If your sister's husband was suckled by the man's milk, then he is the man's son by suckling, and his wife is unlawful for him [the man], because suckling prohibits what lineage prohibits. However, if your sister's husband's brothers were the ones suckled by the man's milk, and your sister's husband was not suckled, then there is no suckling relationship between them, and the man is not a father to him, nor is his wife unlawful for him.