I think the idea that Alexander IV belonged to the same family as Gregory IX (i.e., the Conti of Segni) is no longer current.  According to A. Paravacini Vagliani, Cardninali di Curia e 'familiae' cardializie dal 1227 al 1254, I (Padua, 1972), pp. 41-53, Raynald (as opposed to "Rinaldo") belonged to the family of the counts of Jenne (near Subiaco).  (Though he was still probably related to Gregory IX in some other way...)