Wachstein, Inschriften, pp. 209-210, 263-264 states that R' Meshulam Zalman HaLevi Mirels, A.B.D. Hamburg had a father-in-law named Jakob who was a rabbi in Vienna. The citation is to Da'at Kedoschim, page 48, nr. 2, 2. But Wachstein says there is no evidence of a Rabbi Jakob in Vienna.
Can someone check on this? Also, we need some sources for the two wives of Zalman and their fathers.
Miriam Mirels
Genendel Fraenkel-Mirels-Neumark