Before revision:  Most of their properties run parallel to those of 3 well-studied families: elliptic billiard (confocal pair), Chapple's poristic triangles, and the Brocard porism , allowing us URLanize them in three "similar" groups.
After revision:  Most of their properties run parallel to those of 3 well-studied families: elliptic billiard (confocal pair), Chapple's poristic triangles, and the Brocard porism , allowing us URLanize them in three related groups.