Luiz was born in 1871. He was the son of Thomas Mann. He passed away in 1950.
The English language Wikipedia only references Heinrich's second marriage to Nelly Mann (1898-1944). She committed suicide in Los Angeles. The German language Wikipedia mentions Heinrich's first wife as Maria Kanová, a Czech actress. Need to better understand Nelly's LNAB as there are multiple names put forth. Most likely name at birth seen so far is Emmy Johanna Westphal ... with subsequent alternative of Nelly Kröger ... and then with her married name of Nelly Mann.
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