I believe you want Through the Mirror by Sidhe on Spark rated nc17 would be MA here. It was never completed.

EDIT BY WICCAN: You can find it here on Dokuga with 41 chapters: http://www.dokuga.com/fanfiction/story/3149/1, that's the closest any version is to being done.

This one was an odd one and I don't remember where I read it. I know it wasn't finished when I read it but I still would like to find it.
In the fanfic Sesshoumaru is actually a Tiger demon after his Mother who was abused and killed by Inu Tashio. Sesshoumaru saves Kagome from Hypothermia at the beginning of the story and asks if he can court her. Something about her being his soul mate. He has brothers from his mother's clan who show up and one of them is Sango's soulmate. She is with Miroku and unaware she is pregnant.
That's all I remember, Thank You in adnavce!

Thank you so much! Since I've been stuck at home for the last 3 weeks I've been reading a lot of fanfiction and finding myself looking for older ones I used to read even if they wont ever be finished.