I found two Mendel Kutner's born between the years of 1926 and 1931.
The first name was Mendel Kutner born 15/06/1929 an he lived at Alexhof 48 and Insel 38 11 and changed addresses on 23/06/1942.
The second name was Mendel Leizer Kutner born 23/08/1930 and he lived at Rauch 21 36 and he was deported on 15/03/1942.
I believe the mother of Mendel Leizer was Estera Kutner born 15/08/1899 and his sister was Fajga 25/02/1935. According to the secondary resources if Mendel and his family were deported in March of 1942 they were sent to Chelmno where they perished in the gas vans.
I believe the parents of Mendel born 1929 were Chaim Dawid Kutner born 19/10/1899 and Chawa Kutner born 15/06/1897. His sisters were Cywie born 15/03/1931 and Pesa Ruchel born 15/12/1927 (she also apears as Ruchel Pesa Kutner.)