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.
The Sharee’ah permits the husband to marry up to four wives if he is able to be just between them as we clarified in Fatwas 81469 and 88728.
Moreover, the husband is not obliged to seek the permission of his first wife or his children if he decides to marry a second wife; for more, please refer to Fatwa 86395.
Therefore, your wife and children or any other person has no Islamic right to be angry with you because of this.
Moreover, if it happens that your wife is no longer obedient to you in regard to marital matters and all what that entails, or that she raises her voice at you, then she is a disobedient and rebellious wife and you are no longer obliged to spend on her. Also, she has no rights in regard to you spending the night equally between her and your other wife unless she stops being disobedient. For more benefit on how to treat a disobedient wife, please refer to Fatwa 85402.
If she takes heed after that and becomes righteous, then all perfect praise be to Allaah, otherwise, you should look into the matter of divorcing her but you should not divorce her until you find out what would be beneficial in terms of divorcing her or keeping her. Nonetheless, you should not keep the matter as it is, which is to separate from her and desert her. So, if she does not regain her reasoning after following the means of reconciliation, then you should divorce her in kindness.
Besides, if what you mentioned about your children is true that they humiliated you and stood with their maternal uncle against you, then this is considered from them as cutting ties with you and it is a grave major sin for which they must repent. They should know the status and merits of their father and that it is an obligation to be kind and dutiful to him even if he mistreats them, let alone if he did not do anything wrong in principle and all what he did is a matter which Allaah has permitted.
Also, if it is true that their maternal uncle acted in that manner, then this is injustice and transgression, and it is a clear sin. Even if we presume that you were wrong to his sister by marrying another wife, does this constitute a sound reason for him to do what he did?
In any case, we advise you to be patient, seek the reward from Allaah and be wise.
Allaah Knows best.