All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
It is permissible for a man to marry a second wife whether his first wife agrees or not, provided he can be just between them. Therefore, it is permissible for these sisters to try to find another wife for their brother, and doing so is not an injustice to the first wife if she is safe from being unjustly treated by her husband. In this case, if the first woman supplicates against them, then this is supplicating for a sin and her supplication will not be responded to by Allaah.
As regards a husband not loving his wife, then this should not lead to divorce, especially if the woman is religious and has a good moral conduct. Moreover, marital life is not only established on love as there are many religious benefits which could be achieved through marriage. Furthermore, the husband may marry a second wife and this is better than divorcing his first wife. For more benefit, please refer to Fataawa 85674 and 81469.
If we presume that marital life is not possible between the two spouses, then divorce may be a solution to both of them. Allaah Says (what means): {But if they separate [by divorce], Allaah will enrich each [of them] from His abundance. And ever is Allaah Encompassing and Wise.}[Quran 4:130].