"Και οι δυο αδελφοί;"
It can be pronounced both ways: δύο and δυο (that is δυό, but in this case it doesn't have the accent because it becomes a monosyllable)
Many thanks for taking the time to help. I am wondering why in one sentence the form δύο is used, and in another δυο?
They are equally correct. Maybe in one sentence the "δύο" form was entered first, while in another the "δυο". There is no difference in use :)