Is it permissible to propose to a girl after having married another and having a child, knowing that the family has been forsaken and that this matter may cause harm to the current wife?

It is not permissible to abandon kin, especially over something decreed by Allah Almighty, for Allah says: "And perhaps you hate a thing and it is good for you." It is forbidden for a Muslim to abandon his brother for more than three days, especially if they are relatives. You must return to your relatives and uphold ties of kinship. If polygyny is permissible according to its conditions, then do so. If it is not possible, then distract yourself from attachment to the girl and repel the whispers of Satan. The ruling on passionate love ('ishq) and methods of treating it have been explained in previous fatwas.