On 14 May 1888 at the Lutheran Church, Eastern Hill, Oscar Gustav, eldest son of Carl Gustav Rosengren (161 Gertrude Street, Fitzroy), piano manufacturer married Helena Ross, second daughter of Andreas Pfortner, Esq. of Melbourne. He lived at 34 Michael Street, Fitzroy in December 1888, owned by John Tuttle (Rate Books 1888). This is just before his father passes away in 1889. Oscar continues the Piano business established by his father running it as Rosengren Bros from 317 Swanston St till at least 1890, but piano making had never been a profitable enterprise for his father who was declared insolvent three times in his life, and in 1891, like father, like son, Oscar also is declared insolvent.
Also in 1891 (22 July) Oscar marries again, this time to Emma Amelia Hultgren at St Marks Church Fitzroy. I am not yet sure what happened to his first wife or whether he had children with either.
Oscar then moves into 88 Hanover St, owned by Mrs Cornell in 1892. At 82-86 Hanover a Andrew Hultgren is registered as the owner, which is presumably, Emma’s father. And the following year Oscar and Emma move into #86 and then by1904 he had moved into the larger house at #82 and was still there till 1919 (Rate Books).
All of these houses were demolished in 1960-1970 to make way for the Atherton Garden Estate.