So glad to see this taking off and to reciprocate for others’ lists.
Tell me the one name you think, “Even if you don’t name your third this, you’d be wrong not to consider it.”
2 brothers’ names in usercard.
Current top picks:
Endymion
Rubeus
Taliesin
Ferdinand
Ignatius
Ozymandius
Thelonious
Lucian
Julian
For some reason Ozias came to mind! Literary, unusual and has that same strong O sound as A and H. Also, i think it bridges the gap between Ozymandius and Julian
Ozzy, Oz, O, Zee, Ossy, Zy could be nicknames
(Also, thanks for starting this trend! It’s so fun)
My personal favorite from your list has to be [name_m]Julian[/name_m], but with your boys [name_m]Ignatius[/name_m] would be so perfect. What about [name_m]Aurelius[/name_m]? Shares the “s” ending of Rubeus, [name_m]Ignatius[/name_m], [name_m]Ozymandias[/name_m], and [name_m]Thelonious[/name_m]; has a great meaning; and could go by [name_u]Ari[/name_u] or [name_m]Lio[/name_m] (not sure how these would translate across languages though).
Ignatius seems to work best with your others. However, to keep the io ending trend going, maybe [name_m]Inigo[/name_m]?
I agree with other posters; my favorite is [name_m]Ignatius[/name_m] with your boys. But again, I like all the names you’ve listed.
I’m going to suggest [name_m]Cassander[/name_m]. If not that then [name_m]Cyprian[/name_m]. Cheated again. 
I want to say [name_m]Orpheus[/name_m] because I think it would be a fun twist to have the name start with ‘O’ rather than end with it. But I think it has the right style with very wearable sounds.
I believe [name_m]Ferdinand[/name_m] and [name_m]Ignatius[/name_m] would be perfect for your third child! I also really like Rubeus, [name_m]Julian[/name_m] and [name_m]Lucian[/name_m]. I really like that your two boys have names ending in “o”. Have you considered [name_m]Luciano[/name_m], [name_m]Juliano[/name_m] and [name_m]Ferdinando[/name_m]?
More ideas (Sorry, these are much more names than you asked for 
):
[name_m]Augusto[/name_m]/Augustus
[name_m]Bartholomew[/name_m]
[name_m]Lazarus[/name_m]
[name_m]Octavio[/name_m]
[name_m]Demetrius[/name_m]
[name_m]Cesario[/name_m]
[name_m]Balthazar[/name_m]
[name_m]Marcello[/name_m]
[name_m]Aloysius[/name_m]
[name_m]Roderick[/name_m]
[name_m]Dionysius[/name_m]
Ephigenio
[name_m]Candido[/name_m]
[name_m]Flavio[/name_m]
[name_u]Constantine[/name_u]
[name_m]Antonio[/name_m]
[name_m]Cornelius[/name_m]
Theodoro
[name_m]Lazlo[/name_m]
[name_m]Eustace[/name_m]
[name_m]Fabrizio[/name_m]
[name_u]Thaddeus[/name_u]
[name_m]Orlando[/name_m]
[name_m]Sergio[/name_m]
[name_m]Amadeo[/name_m]
[name_m]Cecilio[/name_m]
[name_m]Mauricio[/name_m]
[name_m]Barnabas[/name_m]
Philemon comes to mind.
Great names!
How about [name_u]Oberon[/name_u], [name_m]Theophilus[/name_m], [name_m]Theomund[/name_m]
Ferdinand/ [name_m]Fernando[/name_m] would go well with your boys.
Of your names I like these: Rubeus, [name_m]Ferdinand[/name_m], and [name_m]Lucian[/name_m].
The name I would suggest is: [name_m]Lysander[/name_m]
Haha. 
[name_m]Will[/name_m] seriously consider:
[name_m]Julius[/name_m]
[name_m]Erasmus[/name_m] (particularly with “[name_m]Elmo[/name_m]” as the nickname!!)
[name_m]Ozias[/name_m] (@Greyblue he has been on my radar before but I agree he is a great middle ground)
[name_m]Aurelius[/name_m] (@dandy_orchid I love Aurèle in [name_u]French[/name_u] but figured it was too weird in the [name_f]English[/name_f] speaking context. [name_m]Aurelius[/name_m] could be a great way to get there!)
[name_m]Inigo[/name_m]
[name_m]Cassander[/name_m] (if Olympias, why not [name_m]Cassander[/name_m]?)
[name_m]Orpheus[/name_m]!!! @elanorelle going along the same theme as [name_f]Proserpina[/name_f] with the whole death/afterlife thing!)
[name_m]Luciano[/name_m]
[name_m]Octavio[/name_m]
[name_m]Aloysius[/name_m]
[name_m]Dionysius[/name_m]
Ephigenio (@Estrela this one is new to me but along the [name_f]Anastasia[/name_f] to Anastasi0 line)
[name_m]Cecilio[/name_m] (always the meaning that gets me on this one)
[name_u]Constantine[/name_u]
[name_m]Cornelius[/name_m] (I used to consider this a top!)
[name_m]Philemon[/name_m]
[name_u]Oberon[/name_u] (@DBrown this used to be top of mind but has somehow faded from sight. Time to bring him back)
[name_m]Fernando[/name_m]/Ferdinando (can’t say I recall even hearing of [name_m]Ferdinando[/name_m] before)
[name_m]Lysander[/name_m] (@TeaJay I don’t know why this one fell off my radar, either).
Thank you all, this was a lot of fun!
I came across the name [name_m]Casparo[/name_m] recently and I think it’d be fitting with your boys! Nicknames [name_m]Parry[/name_m] and [name_m]Cas[/name_m] or [name_m]Cap[/name_m]!