Who is the youngest grandmother?

Supposedly it was Mum-zi a member of a harem in Nigeria who became pregnant at 8 and whose daughter also became pregnant at 8. (1884)

In more recent times, it was Rifca Stanescu at 21, who had her daughter at age 11, and granddaughter when her daughter was 10. (2011)

A 29 year old women who was in 7th grade and 13 when she gave birth to her daughter, and that daughter at the age of 16 just gave birth to a boy.

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26 - http://news.bbc.co.uk/2/hi/uk_news/432463.stm