No, the B-2 was in fact derived from the YB-35 and YB-49; but the YB-35 design predates the Ho229's by several years
Jack Northrop tried to get Douglas to pursue a flying wing bomber design back when Douglas controlled part of Northrop Corp, submitting a proposal as early as 1933, but Douglas balked at the unconventional design and wouldn't fund it. These designs still exist.
When he struck out on his own again in 1939, Northrop once again returned to the eventual YB-35 design, which the US Army officially requested in May of 1941, and Northrop officially submitted - two whole years before the Ho229 was requested
If the YB-35 is directly derived from the Ho229, why is it that the blueprints are older than the Ho229?