How does this work? - Height?

Both their height and your height is a function of genetics. While your parents are average height, your brother and sister especially are quite tall. That fact implies that there are tall genes in your family bloodline. It stands to reason that if they had late spurts that you may also experience some growth later in puberty and allow you to catch up. I recommend talking with your brothers about when they experienced their growth and how tall they were at your age. If I had to estimate, I expect that at the tallest you will be 6ft. I think you will outgrow your 5ft10 sister. Your most likely height is 5ft11 if you experience a late growth spurt.