Is a man's marriage to his paternal uncle's daughter Islamically valid if the man's stepmother breastfed his paternal uncle's daughter multiple times?

The majority of scholars hold that suckling (رضاع) is not established by the testimony of a single woman. The Hanbalis differed, affirming it based on what has been reported from the Prophet, peace and blessings be upon him. What affirms suckling is given precedence over what denies it.