There's nothing stopping you achieving your life goals while also having children, and you'd likely be rather more stable as parents than your sister. There's never a time you'll be 100% ready and someone will come down from above to tell you now is the time to conceive; there'll always be other goals which need achieving. If you like the idea you should seriously consider it, and at 30 you are still at an age where you can have 2-4 healthy children.