Was what I did wrong, and do I deserve this treatment from my brother and the blame from my mother, and was my behavior or my son's behavior wrong towards my brother?

Neither your actions nor your son's actions show any fault that warrants blame or ill-treatment. However, everyone should be reminded of the great importance of kinship ties in Islam. One should be patient with the harm caused by a brother and seek reward from Allah, for the one who maintains ties is not the one who reciprocates, but rather the one who maintains kinship when it is severed. It has been reported that whoever maintains ties with his relatives while they cut him off, and is good to them while they are bad to him, it is as if he is feeding them hot ashes, and he will have a helper from Allah against them as long as he persists in that.