I think it sounds fine that while pursuing your master's degree you are living with your sister and her family. Actually by western standards it's not embarrassing. One of my best friends after her engagement ended, moved in with her brother and his family. In many ways it not only helped her save money while grieving but she was there as support with the kids and helping with housework. They are off on a cruise right now, actually.
Parenting these days is hectic, many people that I know and notice if their siblings aren't actually living with them, they are certainly nearby and offer to help in many ways.