Is it permissible to marry the daughter of one's maternal aunt if she was nursed once with his brother from his mother, and the suckling occurred without the husband's consent?

If your maternal aunt's daughter was nursed by your mother only once, then it is permissible for you to marry her; because the suckling that prohibits marriage is five sucklings. The husband's disapproval does not affect the ruling on prohibitive suckling, and it is not a condition for prohibition that the suckling occur at one time.