Was Mahamaya Prince Siddahrthas Mother ?

Mahamaya is a strange name! Mahamaya means the great illusion .In Buddhist teaching it is vinnana.Mahamaya is supposed to have died seven days after the delivery.The explanation given by Buddhist monks is that Buddhas should not have siblings! (Why ?)

Prince Siddhartha on attaining Buddhahood acquired maha pragna (great wisdom). Great wisdom and great illusion cannot exist side by side. Is elimination Maha Maya (great illusion) giving place to Maha Pragna a riddle in Buddhist scriptures?