Given the reference I've seen tossed around that after the war Lee was opposed to Confederate monuments, I think at some basic level the family has long been aware and accepting of how not only was their ancestor's side was the loser of the war, but what that loss actually meant. Even a simple glance at his postwar politics section on wikipedia suggests he had a really weird, really complex set of values after the war, so the possibility of such values morphing over time through the descendants into something more solidly positive seems... not too out there.
Yeah and they are not that removed from him like they probably knew relatives that knew him.