Answer
(Fatwa: 116/116/M=1432)
In the question mentioned above, the nikah with brother’s wife is lawful, but when you already have wife as it is known by the question, why do you want to marry with your brother’s wife? If you have capacity to maintain equality and justice between both the wives, then you can have second marriage; otherwise you should have only one wife.
And if you mean something else by the family, you can submit the question again.
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband