From Iran's Mehr "News" Agency:
It still remains a question for many people in the UK as how a “flight attendant” could marry Queen’s grandson; a fact that although hushed and ignored by British mainstream media, did not manage to skip some media’s attention.We are then told that Princess Diana was Jewish as well, so William's and Kate's kid will be full blooded Jews!
The truth is that the Royal Family’s new bride is a Jew. Although in the wedding ceremony it was pretended that Kate Middleton is Christian but this lady’s family roots show that she is considered a Sephardic Jew from her mother’s side. Moreover the timing of the wedding and the way it was held which was based on Jewish culture verify the evidences.
Kate’s mother was surnamed Goldsmith before marrying Kate’s father. According to Jewish laws if a mother is a Jew, her children will be Jews, too. Therefore Kate Middleton is a Sephardic Jew and her children will be Jews based on the Jewish law.
Not that there's anything wrong with that. Well, if you are an antisemitic Iranian, maybe there is.
A lot of this seems to be based on this HuffPo piece in 2011, which found the claims to be highly implausible.
(h/ t EBoZ)
UPDATE: More here.