I say Lucet and Tettens are the Divine Twins first of all because I see the Divine Twins in all sets of twins in legend, myth, and folklore. So far, this comparison has held for me, for instance, Caster and Pollox, who RC also lists. RC says Lucet and Tettens are the Twins (not just any twins, but "the") and that they are "brothers and some say one and the same person". The Divine Twins in Feri sometimes function in opposition and sometimes as the same person. Lucet and Tettens are "growth and decay". This parallels well with the Divine Twins, who are Life and Death, Summer and Winter. "One looks forward, the other backward." "One creates, the other destroys" is very much the Divine Twins.
Lucet is "the divine Child". The first of the Twins, takes a very similar role. "Lucet is the King of Light, Fire, Love and Intellect, of Birth and Joy....The Child." The first of the Twins is Light, the second Darkness. All these things describing Lucet fit the first Twin (who is the electron of the first atom, She being the proton that became pregnant and brought forth two, the electron and the neutrino). It's interesting that the Supreme Goddess comes from Lucet's castle.
The second Twin (Winter, Death, Darkness, Destruction) is Tettens. "He is the second twin, the waning sun, Lord over mysticism, magic, power and death, the Baleful destroyer. The God of War, of Justice, King of Kings, since all pay their homage to Him." Just a point I find interesting here: Victor Anderson, the founder of Feri, often talked about the small dark people that he believed were the keepers of the true Craft across the globe. I find it interesting that of Tettens, RC says, "Some say tall and dark, I say small and dark".
I find it interesting that Lucet and Tettens are Fire and Air. These two elements often change around depending on what tradition is using them. This makes sense if they are the Twins. You'll notice that the Twins, and these two elements, are across for each other in the pentagram RC drew.
FFF,
~Muninn's Kiss
(Quotes are from
http://www.1734-witchcraft.org/gillsthree.html)