Many men were involved with the Masons over the years and there has been a lot of controversy about the exact makeup of the group (beliefs, group structure, loyalty system). That's neither here nor there now.
But, more interestingly is that many wives and families became very jealous of the time spent away and the "secrets" that were kept as a part of this organization. You need to think of the era which the great grandfather lived. Thus, there have been many buried that their families intentionally didn't request a masonic service and most likely didn't know about the burial of the apron. Apparently they weren't so opposed to it to keep it around and may have kept it for family history. (One of my grandfathers was a Mason and stories like these did occur more often than thought!)