Should the questioner return to his family in Turkey to care for his disabled sister, despite his pursuit of naturalization and completion of his studies in Sweden, and his fear for her from his brothers and their wives?

You are not obliged to return to Turkey merely because your father said your sister is a trust with you, or because he ordered you to return, if your return would cause you harm. Obedience to parents is not absolutely obligatory; rather, it is obligatory in matters that benefit them and do not harm the child. It is important to note that acquiring the nationality of a non-Muslim country is impermissible except out of necessity, and residing in lands of disbelief entails risks.