Who does sesshomaru end up with?

If you mean as a friend, than that'd be Rin, Jaken, and Ah-Un. Maybe Kohaku as well. He likes InuYasha and his group, although the 2 brothers don't get along. In a love kinda way, he is somewhat in love with Kagura.

Contradicting to that last statement, it seems as if Sesshomaru and Rin would be a better pair than Kagura and Sesshomaru.

The presence of Rin at his heels is proof of his growing compassion. He not only tolerates a human, but also acts in an extremely protective manner towards her and rushes to her aid when she gets in trouble.

And, it is actually the other way around with Kagura. She seems to hint romantic interest in Sesshomaru, but she dies anyway. (Spoiler).