His brother Leopold Eidlitz was a well-known architect, as was Leopold's son, Cyrus L. W. Eidlitz.
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Cyrus Eidlitz was the nephew of the noted builder Marc Eidlitz of Marc Eidlitz & Son Builders N.Y.C. and the grandson of the architect Cyrus Warner (who was the father of architects Samuel A. Warner and Benjamin Warner).
Leopold's brother Marc Eidlitz was the founder of a major construction firm, Marc Eidlitz & Son Builders N.Y.C. in New York, which built the St. Regis Hotel and many other projects.