I suppose it’s a spoiler for mentioning this (since the official site makes no mention of it), but the new title from Astronauts has twincest in it.
That sounds fun, I’d be interested int that if it got translated.
A release from last year, as the title obviously states, has twincest in it: Kurano-kunchi no Futago Jijou from Cube. It’s the brother-sister type, so comparisons to Yosuga no Sora will be made, justified or not: including but not limited to the sibling’s silver hair and sister’s tsundere persona.
Narg, this might be relevant to your interests: the otome-ge Under the Moon apparently features twins. The protagonist is the girl with the blue ribbon. (There’s also a pair of boy twins as love interests, with separate endings each and a 3P ending.)
i hope jast usa translates that game some day
play dual phase and it will change your mind
Narg has been a very bad person for not updating this most glorious of glorious threads more often. 
On the bright side, it looks like 2014 won’t be devoid of twincest. 8)
Houkago no Futekikakusha from Nostalgic Chord. Looks uninteresting though.
http://www.getchu.com/soft.phtml?id=790480
Love Love Life from Pajamas Soft. Standard issue sexfest.
http://www.getchu.com/soft.phtml?id=788987
Clover Day’s from Alcot. Now this seems promising. Prequel story to Clover Heart’s.
http://www.getchu.com/soft.phtml?id=783217
On the anime side of things we’ve got the second season to Date A Live. Dem delicious Yamai twins are so yummy. :twisted:
but not quite, i’m sorry
If Narg wasn’t into Vocaloid, this may change things :mrgreen:
I believe that’s formally known as Pinecest.
Don’t ask how I know. 
I certainly hope someone will bring this thread over to the new JAST USA forums.