I Caught My Brother's Wife Using Him Like A Houseboy

I went to my elder brother's house for a visit and I lost my peace due to what I saw there. I didn't call him on phone before going, I knocked and their first son opened the gate for me, when I entered they were eating. Normally the woman was supposed to dish food if they needed more but to my greatest surprise she asked him to dish more, like an obedient servant he went to the kitchen to get more.

About 30 minutes later her younger sister arrived and the wife started sending him all manner of errands, she started with bring yam for Mercy (the name of the girl), he brought the yam and she sent him again to tie the yams together for the girl, I was pissed.

As a lady myself, I couldn't believe my brother was doing that. She later send him to their shop to bring some stuffs for the girl, I left immediately cos I couldn't bear it any longer. The girl is above 20.

Should a man accept such from his wives...to be treated as errand boy? Is this even clear eyes?