Majer may be his younger brother. In the students list there is only one other student with the last name Klepacz and they have the same housing addresses while in the ghetto and the same transport number. There is also a man born in 1903 named Mojszer Klepacz who was born in 1903 and has the name first address as Majer and Mendel while int he ghetto. He also has transport number 5 I believe that this is either their father or another family member. I may have also found the mother Dwojra Klepacz. When I searched the database for klepacz she was the only women who came up with the same two address as Mendel as well as the same transport number. It says she was born in 1904 therefore if she is his mother, she would have been 24 when she gave birth which was not an uncommon age to be married and having children at that time.