The term 'social philosophy' does not have a fixed meaning in current philosophical circles.
Social philosophy becomes in good part an ontology of social science.
Consider an analogy. The philosophy of mind seeks to tell us what is involved in a creature's being a psychological subject, as social philosophy tries to say what is involved in an arrangement's being a social form of organization. In raising the psychological question, the philosopher will take account of all that we know, in our experience of ourselves and others, of human psychology. But if he is serious, he will also take account of what the best psychology and neuroscience, as he sees it, says about psychological subjects. We should note, in passing, that the stock of commonplaces that a social philosopher recognizes may vary, depending on the scientific verities that he recognizes.