Is the journey undertaken for the purpose of visiting one's father and sisters considered maintaining ties of kinship, for which shortening prayers is permissible? And is it obligatory to re-perform the prayers that were shortened based on this interpretation?

A traveler on a permissible journey is allowed to shorten the four-rak'ah prayers. If the distance is approximately 83 kilometers, it is permissible to take advantage of the concessions of travel. Shortening the prayer is better than performing it in full. The duration for which one can shorten prayers is less than four days. It is not a condition for shortening and combining prayers during travel that it involves maintaining kinship ties; rather, it must simply be a permissible journey. Your travel with your father to gladden his heart is considered an act of righteousness and maintaining kinship ties. We advise you to turn away from doubts, lest they transform into obsessive whisperings (waswasah).