The most popular hadith quoted, when the topic of polygyny comes up, seems to be this:
Anas relates that the Prophet (peace be upon him) said: “None of you truly believes until he loves for his brother what he loves for himself.” [Sahîh al-Bukhârî and Sahîh Muslim]
It is usually a reminder to the women, the existing wife/wives and the new wife so they will be kind and generous with each other...and with the sharing of their husband. I am a big proponent of this concept, mashaa'Allah, so please don't misunderstand what I write next.
The hadith is for everyone, men and women alike. So, what happened to the brothers?
Consider the man with a plate full of food and a man beside him, hungry with no food. Is reaching out and taking another plate of food, leaving the man beside him without, loving for his brother what he loves for himself? What, then, of wives? When there are so many brothers looking for good wives, don't the discerning ones who are looking for second, third, or fourth wives ever think that if the woman meets their criteria for marriage, that she probably meets the criteria of a single brother? Do they consider that in recommending those prospective wives to unmarried brothers, they are removing a stress and discomfort from their brother? They have the chance to facilitate for their brother what they already have, the other half of their deen and a guarding of their private parts. Wouldn't that reap a huge reward? Isn't that putting the hadith into real practice?
In addition, for those men with daughters of marriageable age, are they eager for them to enter polygyny? Do they believe it is a better and more pleasant life than monogamy? No question, there are wonderful advantages to being in polgyny. However, most would agree that polygyny is a test and shaytaan's favorite workplace - not easy and often painful. Is marrying a daughter into that (rather than to another suitable, unmarried man) loving the best for her? Perhaps, sometimes. More often though, the answer will be no.
Before I am attacked with a load of scenarios which don't fit this mold, let me say that I know it isn't a one-size-fits-all viewpoint. I am not making a blanket statement, just reminding of a certain aspect. There are many situations where taking an additional wife is the option warranted by Allah; it is a beautiful Sunnah. Certainly, some women are better suited to be in polygynous marriages or don't find single men in their age group or community to marry. However, in polygyny the loving for your brother what you love for yourself needs to be considered and implemented by both sisters and brothers.
May Allah be the Governing Force behind all our intentions and actions - ameen.