What do you think about two brothers named Zach (Zachary, but called Zach) and Jack?
Do you think it's too close? Do you have any of your own family or friends experience, where two siblings would be named like that?
I can think of John and Joan Cusack (although, there are a couple more siblings).
Also Joy-Anna and Johanna Duggar.
If twins are named Christopher and Christian and Isaac and Isiah, why wouldn't two siblings be named Zach and Jack?