Hisui

Miroku and Sango's son was their first (And presumably only) son.

History
Miroku and Inuyasha were off exterminating a demon while Sango was giving birth to her third child. Rin and Lady Kaede were present during the birth. The birth had been successful by the time Miroku returned to his family.

Physical description
Miroku and Sango's son was a small, newborn baby. He had a small tuft of light brown hair atop his head, and his skin matched the light tone of his parents.

Trivia

 * His name is not revealed along with his older sisters.
 * In the one shot manga special, InuYasha Since Then, he is now six months old and is shown to resemble his father.