Interesting ideas, laced with humor. Just what this list needs.
My own opinion on the matter of sidhelien numbers comes from stuff I
picked up somewhere. I read that elves had a longer gestation period
(something like 27 months?). Anyway, I guess that was based off of their
longer lifespans, so if that takes longer, maybe it's a lot harder to get
pregnant, and also more likely that elven females are less willing to get
pregnant, as well as more open to miscarriage risks along the way.
The gheallie sidhe and the "welcoming" of half-elves to elven societies
are contradictions, but I submit that comes from differences of
opinions/attitudes among the elves. Some elven realms (that is, the
"mainstream" of society) are more likely to accept half-elves (and also to
generate half-elves?), such as Tuarhievel and Cullabhie, while others
(Sielwode, Rhuobhe, Lluabright) would not, and might even banish them from
their lands. Some might also decide that (forgive the pun) "half an elf is
better than none" and raise them in hopes of creating a valuable (to elf
society) person.
So, the question comes up, where are all of these half-elves coming from?
One source is "friendly" elves and non-prejudiced humans. A second is that
two half-elves make another half-elf, and maybe they are a bit more fertile
than "full-blooded" elves. Finally, maybe half-elves live longer, and they
just stick around more. I ruled that if elves in BR are "immortal," then
half-elves use the PHB aging tables for full elves, not half-elves, thus
living hundreds of years.
Looking at two specific cases, perhaps the Baroness of Dhoesone and
Savane's child are results of strategic decisions among the Tuar royal family
to start recruiting/breeding relatively long-lived allies among their
neighbors. The child of Savane is still a grandchild of the Mhor, and can
greatly complicate any succession struggle. IMC, one of the players (druid-
fighter, no less) is a (secret) son of another Tuarhievel noble, a half-
brother to Rhuimach Taeline. He and I are still exploring what this really