Gender: boy
School:
School #20A
The person I found was at the right age to attend the school, his occupation was Schueler. According to the JewishGen database Berl could be a nickname for Berek.
Chaskiel Makower lived at the same Ghetto address. He was born two years before Berl, so he is most likely his older brother. Also, there are two more people listed under this address: Sara Makower, born in 1906, and Szlojma Makower, born in 1905. One of them is probably Berl's and Chaskiel's mother.
I just found that Szlojma Gakower ist listed as Male, whereas Slzojma Makower is listed as Female. But we can assume that this is Berl's father and Sara was his mother. Also, all the other Szlojmas I found in the database are male which indicates that this is a male name.
In the Yad Vashem Central DB of Shoa Victims names I found a person with the name Dov Berl Makower. He died when he was 9 years old and lived in Warsza. But, I am not sure if this could possibly be the same person.