A Shakespearean sibset! Oh, how brilliant! 
[name_f]Cressida[/name_f] and [name_f]Octavia[/name_f] are so grand, I feel like [name_m]Cassius[/name_m] and [name_m]Maximus[/name_m] are the better pairings with them, but I worry that [name_f]Cressida[/name_f] and [name_m]Cassius[/name_m] would get confusing after a while. [name_f]My[/name_f] nephews have similarly sounding nicknames (0llie and Alf!e) and [name_f]Cressida[/name_f] and [name_m]Cassius[/name_m] feel a bit like that to me. I feel bad every time I call my nephew his brother’s name lol. [name_m]Cassius[/name_m] is my favorite of these names in general, but because of that, I’m wondering if [name_m]Justice[/name_m] or [name_m]Maximus[/name_m] would be the better option. Because of that… I think I’m actually voting for [name_m]Justice[/name_m]? I didn’t expect it, but it seems like the most distinctive, plus I love the idea of all three of them having a [name_m]Shakespeare[/name_m] name. I’m not sure about a nickname, maybe depending on the middle name, you could do something like [name_m]Justice[/name_m] [name_m]Lionel[/name_m] nn [name_m]Jules[/name_m] or [name_m]Justice[/name_m] [name_m]Desmond[/name_m] nn [name_m]Jude[/name_m]?
Good luck!