Board Thread:Improvements and Issues/@comment-6961916-20130306114004/@comment-26420452-20131222074715

That doesn't necessarily mean that they're not related. You can be from different families and still be related (by the maternal sides). See, in order to maintain blood purity a lot of intermarriage goes on. And this is speculation, but the Kurosaki and the Ishida were probably the only two Echt Quincy families in Japan.