Dubin, David M. MD
In my tree I have a Yitzchok and and Ayzik who were brothers, both alive at the same time. Both correspond strongly with Isaac.
I was given my a Jewish name, Meir David, while my grandfather Yitzchok David was alive.
it’s pretty clear two brothers would not have the exact same Jewish/Hebrew name. (George Foreman notwithstanding)
some possibilities include:
Finding the birth records would help greatly.