Liepmann had the following children by his first marriage: Naphtali Hirz (died 1709), who became president of the congregation; Moses Jacob (died 1697), praised as a Talmudic scholar and philanthropist; Gumpert and Isaac, who, in 1721, were accused of an attempt at fraudulent bankruptcy, in consequence of which they were compelled to leave Hanover (1726).

Behrends' daughter Genendel became the wife of the chief rabbi of Prague, David Oppenheim.

He stood in close relation to a number of princes, assisted Talmudic scholars, and established a bet ha-midrash in his own house.

The library of his son-in-law David Oppenheimer, which he had himself enlarged, and which his son-in-law, owing to censorship and other reasons, did not wish to keep at Prague, was removed by Behrends to Hanover, thus enabling the pastor Johann Christoph Wolf of Hamburg to avail himself of it in preparing the Bibliotheca Hebræa.

The fate of Liepmann's two sons Gumbert and Isaac is related in a family megillah, published by Jost in the second volume of the Jahrbuch für die Geschichte der Juden.