Gender: girl
I may have found Mirim's brother, uncle, or other male relative. Dawid Znamirwoski is a match for last name and address, and his year of birth, 1917, would have made him twenty-four years old in 1941 when Miriam signed Rumkowski's book.
I feel that I have found Miriam's father. I searched the database using the last name Znamirowski and found a man, ABRAM SZLAMA ZNAMIROWSKI, who is a match to Miriam in address. He was born in 1892, moreover, which would have made him thirty-five years old in the year of Miriam's birth.
Finally, I think that I may have found Miriam's mother. EWA ZNAMIROWSKI's address matches Miriam's. She was born in 1891, making her thirty-six years old at the time of Miriam's birth.