They'd make interesting pair if they turn this anime into a soap opera sort. Like in between Final Act series and Yashahime series, all in temporary, Sesshomaru/Kagome/Inuyasha love triangle might happen while Rin and Kohaku happen at a same time. Yeah, I know this never happened, but just an interesting fanfictional idea.
It was just a friendly thank you kiss and Sesshomaru didn t sleep with her he just warmed her up with his mokomoko because she had taken a bath in the forest.
