Mitsuba Monogatari - Vol. 1 Ch. 4 - You Are Mitsuba

[Tamed]

Given how he obsessed he was on 'reviving' mitsuba i'm surprised he even had a second wife (unless she was a concubine or arranged marriage with a noble family his parents got along with lol)

Second wife was for political reasons. He was required to produce an heir for the scepter and at the time, people thought that Mitsuba's mom was barren.