Not only but also structure as a correlative conjunction
Not only are they my family, but they are also my close friends. In this structure, you need to use the correlative conjunction, ‘not only, but also’ in the correct and appropriate way. Since not only is located at the start of the sentence, you need to use inversion in that sentence. That is, you need to use a question form instead of a statement, although it does not have any interrogative function.
It’s so rewarding to hear that you’re going to reciprocate their kindness and favor in the future. In spite of their unconditional love and care, you’re consciously and mindfully determined to return their favor, which is so great.