My brother has type 1 diabetes. Should I be worried about this?

Probably not. Although it is possible, it is actually unusual for there to be more than one type 1 diabetic in the immediate family. There is a hereditary component but there needs to be a trigger and if you have not been subjected to the trigger - whatever it is - you will not develop the disease.
Yes. Since family history (in other words, your family's genetic makeup) is a major influence in whether members of the family are at risk of developing diabetes - either type 1 or type 2, you should be aware that you all are at some increased risk. Discuss the symptoms of disbetes with you physician and research information on websites like the american diabetes association.