Are my aunt's children, whom my aunt did not breastfeed, considered my siblings, and must I maintain kinship ties with them?

If a woman breastfeeds a child under two years of age five or more satisfying times, he becomes her son through suckling (رضاعة), and her children become his siblings through suckling. However, maintaining ties of kinship (silat al-rahim) is not obligatory for siblings through suckling, nor for the children of one's paternal aunt.