I love the nn [name_u]Koa[/name_u] for a boy and I also have the nn [name_u]Kai[/name_u] for a boy or girl as well and I think it would be cute if they were twins
For a boy I have [name_m]Malachi[/name_m]/ [name_m]Malakai[/name_m]- nn [name_u]Kai[/name_u]
For a girl I have [name_f]Kailani[/name_f]- nn [name_u]Kai[/name_u]
And then I love [name_u]Dakota[/name_u]-nn [name_u]Koa[/name_u] but where I live I can only use it as a girls name so I am looking for a boys name that is long and could have [name_u]Koa[/name_u] as a nn
Some ideas I have (some more of a stretch than others):
Kekoa
[name_u]Kainoa[/name_u]
[name_m]Jacoby[/name_m]/Jakoby or [name_m]Jacob[/name_m]/Jakob
[name_u]Kodiak[/name_u]
[name_u]Kolby[/name_u]
[name_m]Nicholas[/name_m]/Nikolas
[name_u]Rocco[/name_u]
[name_m]Nakoa[/name_m]
However, I think [name_u]Koa[/name_u] is best standalone. I think you could totally have a [name_u]Kai[/name_u] and [name_u]Koa[/name_u], with [name_u]Kai[/name_u] being short for something and [name_u]Koa[/name_u] being standalone.