Will I be sinful for the estrangement from my brother that was caused by his wife?

You must make an effort to mend the relationship between you and your brother, even if the estrangement is from his side. This is part of maintaining kinship ties, which is an obligation by consensus. Remind him of the sanctity of kinship and the sin of severing it, and be patient with his estrangement and ill-treatment. For the one who maintains ties is not he who reciprocates kindness with kindness, but rather he who connects with those who cut him off and does good to those who do him ill, as the Prophet, peace and blessings be upon him, said: "The one who maintains ties is not the one who reciprocates, but the one who maintains ties is he who, when his kinship is severed, he connects it." By doing so, you will attain Allah's pleasure and help, and you will have a supporter from Allah against them. If you exert your utmost effort and he does not change his stance, then there is no blame upon you, and continue to make efforts from time to time.