Is seeking a divorce after an unhappy marital life and having two children considered forbidden (haram)? Is it necessary to seek forgiveness for it while feeling regret? And is it required to seek permission from the former husband to marry again?

If a woman seeks divorce due to her husband's ill-treatment and injustice, there is no blame upon her. However, if her request is without a legitimate Islamic reason, she has erred and must repent by feeling remorse, resolving not to repeat the act, and increasing good deeds. There is no need to seek permission from a former husband to marry someone else, as he is a stranger to her. But if she wishes to return to him and he has not divorced her three times, there is no impediment to having someone intercede and present that to him.