Opinions please!

I am writing a story with two of the main characters currently being called [name_f]Amelia[/name_f] and [name_m]William[/name_m]. However I have since realised that whilst their primary nicknames are [name_f]Mia[/name_f] and [name_m]Will[/name_m], their other nicknames are [name_f]Millie[/name_f] and [name_u]Billy[/name_u]. And now I think they are too cutesy to go well together. [name_f]Amelia[/name_f] is definite however what could you suggest to replace [name_m]William[/name_m]? I have considered [name_m]Samuel[/name_m] “[name_u]Sam[/name_u]”, [name_m]Nathaniel[/name_m] “[name_m]Nate[/name_m]” and [name_m]Gabriel[/name_m] “[name_m]Gabe[/name_m]” but nothing seems to work.
What do you guys think?

[name_f]Amelia[/name_f] and [name_m]Samuel[/name_m] or [name_f]Amelia[/name_f] and [name_m]Oliver[/name_m]

Why are you using so many nicknames? Most only use one for a child that actually goes with their name… then maybe pet names that have nothing to do with their names. [name_f]Millie[/name_f] & [name_m]Will[/name_m] could be the nn: not many go by “[name_u]Billy[/name_u]” these days…