Boris Becker – the famous former several time Tennis World Champion – is often assumed to be a German Catholic, which in a sense is true.
However, delving a little bit of his biography reveals that his Czechoslovakian mother Elvira was in fact jewish (1) or rather ‘had jewish relatives’. (2) This would mean that in halakhah – i.e., jewish religious law - and according to the Israel Law of Return; Becker would be jewish.
‘Ethnic Celebs’ quibble that it is ‘not clear’ if his mother’s ‘jewish relatives’ are converts (3) may be taken with a pinch of salt precisely because conversion in Judaism is extremely unusual throughout its history, while conversion to Christianity among jews has always been a significant minority behaviour among the jewish population.
Therefore, on the balance of probability and no other evidence; we have to say that Becker’s mother is from a family of jewish converts to Catholicism not non-jewish converts to Judaism. So thus, Boris Becker is indeed jewish according to both halakhah and Israeli law.
References
(1) http://www.nndb.com/people/231/000023162/
(2) http://ethnicelebs.com/boris-becker
(3) Ibid.