Shah Jahan had other wives as well. Including Qandahari Mahal and Akbarabadi Mahal. But according to court historians, these marriages were based on political alliances. Various historical accounts tell us that Shah Jahan’s relationship with his other wives, were marriages only in name. They were simply to maintain political alliances.
Shah Jahan’s affection and love for Mumtaz was much more than that for his other wives. This is why she was given more favours. Such as the title of Malika-i-Jahan, the ‘Queen of the World’. Her palace, Khas Mahal, was said to have been decorated with pure gold and precious stones. According to historical records, Mumtaz showed great interest in administration as well.
So when Shah Jahan went for diplomatic negotiations, or for war, Mumtaz always accompanied him. Shah Jahan had exactly one child with all his other wives, with Mumtaz Mahal, he had 14 children.
Half of the children died during childbirth. This used to be much more common back then. The healthcare system used to be terrible. Unfortunately, Mumtaz died while giving birth to their 14th child. It happened on 17th June 1631. The cause of death is said to be postpartum haemorrhage, Loss of blood.