Caspian [name_m]Felix[/name_m] or [name_m]Atticus[/name_m] [name_m]Elijah[/name_m] fit best to me 
I’m back again with a new list.
Atticus “[name_m]Ace[/name_m]”, “[name_f]Atta[/name_f]”, “[name_m]Ty[/name_m]”
[name_m]Felix[/name_m] “Flix”, “[name_u]Eli[/name_u]” but most likely just “[name_m]Felix[/name_m]”
[name_u]Luca[/name_u] “[name_m]Luc[/name_m]”, “[name_u]Lux[/name_u]”, “[name_u]Lucky[/name_u]”
[name_u]Ezra[/name_u] “Ez”, “Ezzy”, or just “[name_u]Ezra[/name_u]”
I realized that I probably can’t have everything from my wishlist – a unique but recognizable boy name with 6 letters and a 3 letter nickname for everyday use… that also hasn’t been used by a friend or family member. LOL So, I have started to adjust my expectations and just find something nice regardless of length or nicknames. I have not fallen in love with any name yet, but we are warming up to [name_m]Felix[/name_m].
Here’s the rest of my list:
[name_u]Asher[/name_u]
[name_u]Atlas[/name_u]
[name_m]Apollo[/name_m]
[name_u]August[/name_u]
[name_u]Kai[/name_u]
[name_u]Koa[/name_u]
[name_m]Leon[/name_m]
[name_u]Levi[/name_u]
[name_m]Malachi[/name_m] / [name_m]Malakai[/name_m] - I love the nickname “[name_u]Kai[/name_u]”!
[name_u]Orion[/name_u]
[name_m]Orson[/name_m]
[name_u]Rylan[/name_u]
[name_u]Rowan[/name_u]
[name_m]Ronan[/name_m]
[name_m]Xavier[/name_m]
Caspian, [name_m]Soren[/name_m], [name_u]Phoenix[/name_u] have been taken off the list for now.
Another vote for keeping [name_m]Caspian[/name_m] in your top three 
Something with an A or N in it!
From your list, I think [name_m]Caspian[/name_m] may fit your sibset the best. [name_f]My[/name_f] second pick would be [name_u]Rowan[/name_u] (even possibly [name_u]Rowan[/name_u] [name_u]Atlas[/name_u] [LN]).
Simon also popped into my mind when I saw your first two kids’ names.
My very favorite type of name! In fact, my three boys have names in that category:
[name_m]Sebastian[/name_m] “Bash”
[name_m]Conrad[/name_m] “[name_m]Rad[/name_m]” (Six letters with 3-letter nickname!)
[name_m]Truett[/name_m] “[name_u]True[/name_u]”
Your kids’ names are gorgeous, and I’m sure you’ll select something wonderful for your new little guy.
I love [name_m]Lucas[/name_m]. And maybe [name_m]Lucas[/name_m] [name_m]Xavier[/name_m] could go by [name_u]Lux[/name_u]?
Have you considered [name_m]Lucian[/name_m]/[name_m]Lucien[/name_m] to get to the [name_m]Luke[/name_m]/[name_m]Luc[/name_m] nickname? Best of both worlds, really, as you could use [name_m]Ian[/name_m] as well.
Yes! I thought we would use [name_m]Lucius[/name_m] / [name_m]Lucian[/name_m] because it meets my criteria and has a great nickname. DH said he would just prefer “[name_m]Lucas[/name_m]” after all
I don’t see many standing nickname options for [name_u]Rowan[/name_u] or [name_m]Atticus[/name_m], so I would cut those.
I love [name_m]Lucas[/name_m] “[name_m]Luke[/name_m]”! It’s sad that that it’s so popular, [name_u]Luca[/name_u]/Luka is also cute. [name_m]Caspian[/name_m] might have the nickname Aspan/Aspen (although it IS a stretch) which I think is really nice as well.
Luca [name_m]Leo[/name_m] I nice, especially if you are pronouncing [name_m]Leo[/name_m] as lay-oh.
Ahhhh, I see. [name_m]Lucas[/name_m] is still a great name though!