Futago Okami tachi Futago is twins and Okami tachi is wolves
'Twin' in Japanese kanji is双子 (futago).
Imōto no futago no imōto
depends which one is born first. the one born first is the younger, as it went up there last according to Japanese beliefs, so to our way of thinking, the older twin would call the younger twin onisan or anesan (boy or girl) and the younger one or second born twin would call the other ototo or imoto (boy or girl)
オオカミの土地 Ookami no tochi
'Twin tigers' is双子のトラ (futago no tora) in Japanese.
'Twin boys' isåŒåã®ç”·ã®å (futago no otoko no ko) in Japanese. An alternative to this would beåŒåã®å…„弟 (futago no kyoudai) which means 'twin brothers'.
Ookami.
"Ookami" means wolf.
futago
Possibly Futago no Tamashii Futago - (a) twin Tamashii - Soul
Don't worry so much about a title -- if you publish the story, the editor will call it whatever they want. Click the link for help.
双子 /fu ta go/ means 'twin(s)'. Used as a modifier, like 'twin daughters' there is need to add a の /no/, so it would be 双子の娘 /fu ta go no mu su me/.