Is the husband of the foster aunt considered a forbidden marriage (mahram), given that the wife (the aunt) did not nurse the father, but rather nursed some of the paternal uncles?

This woman is your paternal aunt through suckling if she suckled from you five رضعات (sucklings) within the first two years of her life. She is a mother through suckling to any of your paternal uncles who suckled from her. As for her husband, he is not your paternal uncle; rather, he is the husband of your paternal aunt through suckling and is not a forbidden relative (mahram). However, it is unlawful for him to be married to you and your paternal aunt through suckling at the same time, due to the Prophet's (peace be upon him) saying: "What is forbidden by lineage is forbidden by suckling."