There is no Sin Upon You if You Love One of Your Wives More Than the Other
Question :
I am married to two wives all praise and thanks be to Allah and I fulfill all of my responsibilities towards them, but one of them is more obedient to me and behaves better towards me than the other, which has created an inclination in me towards the first. Is there any sin upon me in this?
Answer:
It is incumbent upon the husband to act with fairness. between his wives in everything he can. As for the things. which he is unable to do, there is no sin upon him in that, according to the Words of Allah, Most High:
"Allah burdens not a person beyond his scope."
and also the Words of Him, Most High:
"So keep your duty to Allah and fear Him as much as you can."
So if the questioner loves the wife who fulfills her obligations towards him more than the other, who neglects her obligations towards him, then there is no sin upon him in that. But he should not neglect being fair in the rights of the second wife in all that is possible.
Source:
Ibn 'Uthaimin
Fatawa Islamiyah, Vol. 5 Pages 363-364