naynaynrw
inuyasha and him have the same mom.
No, Inuyasha and Sesshoumaru only share the same father. They're half brothers, and thus have different mothers. Since Inuyasha is a half demon, his mother was human, who died many years ago. There's actually no canon source of when she died, BUT Rumiko Takahashi did let slip quite early in the series (long before the third Inuyasha movie, Swords of the Honorable Ruler, which is completely
wrong in accordance to the series) that Inuyasha's mother died before Midoriko was around, and keep in mind in the manga and anime, both said that Midoriko lived over 400 years ago.
Sesshoumaru's mother is still alive, as she's a full dog demon after all. She does make an appearance in the manga, I believe around the 460-70's chapters. Unsure as I don't have the manga open right in front of me to check. The post above as the picture of her directly from the manga so I'm sure that's good enough. Her name however is not Sakasagami. Rumiko never gave her a name. In fact, Rumiko has a big problem with never naming the parents of the characters in her series. The names given to Inuyasha's mother, and Inuyasha and Sesshoumaru's father were names the creators of the third movie came up with, because they realised it would be weird if they avoided referring to each other by name.
Although it doesn't show us so much about Sesshoumaru's mother. We only know that she's a full dog demon, who is living in a palace in the clouds (therefore, she is still considered to be a noble demon). It appears like her only child is Sesshoumaru, so that rules out the possibility of "long-lost siblings" for those fans who keep insisting. We don't see much of her abilities, other than the dog transformation, which is standard for dog demons, and her power over the Meidou-Seki. As those chapters mainly focused on Sesshoumaru, the most we see of her personality is Jaken commenting (mentally) that Sesshoumaru must have gotten his cold personality from her, and we also see that she has a bit of a teasing nature as she has made some few light jabs towards her own son. It wasn't exactly stated, but there is some implication that her and the Inu no Taishou were married when he passed on, and it was really only by the way she spoke of him. So it's unlikely they divorced- and keep in mind marriages during the Feudal Era were life time committments! Divorce was NOT an option.
Admittedly, there is quite a lot that needs to be explained, like if she knew about her husband's other wife and son, or if she even knew that her own son was planning in stealing his father's sword. Also makes you wonder about her age, and what was her true relationship with her husband, and if she hadn't seen Sesshoumaru for a long time does that mean he lives in his own place or has he just "ran away" from home for that long? There's a lot about his mother that Rumiko failed to answer, and worst of all, evoked even more questions. It was probably apart of her plan to keep the fans guessing.