Complex sentence: During this power struggle, Dara Shikoh received the support of his oldest sister, Jahanara Begum while Roshanara Begum sided with Aurangzeb, instead.
Split into simpler sentences: During this power struggle, Dara Shikoh was aided by his oldest sister, Jahanara Begum. One of the many younger sisters, Roshanara Begum, sided with Aurangzeb, instead.