Friedrich MARX married his 3rd wife Ernestine GERBER (we do not know the names of his other wives and their children)
The Heymann and Marx families are related through the Gerber Family. Ernestine and Johannah Hermine, who married Adolf Heymann, were sisters.
The Gerber family trace their lineage back through  the Oppenheimer family to the famous Rabbi Judah Lowe (the Maharal of Prague) and then back to King  David (King of the ancient Kingdom of Israel0
Their son Bernhard migrated to New York, where he became a CPA Certified practicing accountant.

Bernard Marx's Letter of principle supporting Jews of Germany against the Nazi's (Click here)
Bernhardt Marx moved to Fort Lee New Jersey. Bernard was a major supporter of the Teanach Reform Congregation.

His children Fred  and Carlene still live in New Jersey.

Fred married Adele Gotlieb and had 2 boys David and Daniel. Fred took over Bernard's CPA practice.
Fred was a founding member of an Orthodox Congregation Ahavath Yisroel (with much support from Chabad Lubavitch). For a period Fred was the President of Ahavath Yisroel congregation .

Carlene married Seymore Fleishman from Brooklyn New York.
They have 2 sons Stephen and Robert.
Carlene became very active in the Teanach Reform congregation, and its President.