from what ive gathered: the twins' names are takahito and kizuki.
enjou is about takahito who inherited the 'eve' trait from hayato (he can birth babies too) so some englishman kidnapped him to have his children.
retsujou is about the other twin kizuki. that's all i know about it for now.
the current leader of the ookami clan is takao (hayato's little brother; the seme of the glasses sensei from hatsujou)
where can i read the novel?
its called affection: call of the king in english, someone started translating it last two months ago
https://himikochou.wordpress.com/novels/
thank you(⌒▽⌒)
there are 4 light novels about their twin baby cubs who also happen to be gay (enjou volume 1&2 and retsujou volume 1&2)
hatsujou: takao X glasses sensei
yokujou: hayato X enemy yakuza
mitsujou: hayato has twins
enjou: youngest twin x british guy
retsujou: oldest twin x ???