I am having boy twins and am looking for a brother name to match this one. I don’t mean to match like [name]Jayden[/name] and [name]Jordan[/name], but more like that they sound in the same style… The way [name]Eleanor[/name] and [name]Beatrice[/name] would.
I like A-C, E-F names.
I thought of [name]Henry[/name] first. Maybe [name]Edward[/name] or [name]Everett[/name]? Style can be a pretty subjective thing though. What I think matches in style may not be your matching style. 
[name]Just[/name] some suggestions for you though.
[name]Frederic[/name]! I’ve always thought [name]Charles[/name] and [name]Frederic[/name] were the perfect twin or brother names! Other suggestions, using the letters you listed:
[name]Arthur[/name]
[name]Alfred[/name]
[name]August[/name]
[name]Abram[/name] (might be a stretch)
[name]Alvin[/name]
[name]Alexander[/name]
[name]Benjamin[/name]
[name]Blaine[/name]
[name]Conrad[/name]
[name]Cedric[/name]
[name]Colin[/name]
[name]Calvin[/name]
[name]Callum[/name]
[name]Elias[/name]
[name]Everett[/name]
[name]Ephraim[/name] (again, might be a stretch)
[name]Edward[/name]
[name]Edmund[/name]
[name]Edwin[/name]
[name]Edgar[/name]
[name]Francis[/name]
[name]Frank[/name]
[name]Felix[/name]
[name]Fergus[/name]
I know you stated specific letters, but I thought I’d also throw out that I adore both [name]William[/name] and [name]Henry[/name] as brothers to [name]Charles[/name]. Good luck!
these are great suggestions. And I agree with the above poster, style is somewhat subjective but what I am going for with “style” is like… traditional vs indie etc. etc. I especially like the A names. Thanks for the feedback folks. Anyone else have some suggestions… maybe starting with A?
[name]Alan[/name] springs immediately to mind as a classic that isn’t on the upswing but isn’t strange-feeling. [name]Charles[/name] and [name]Alan[/name].
[name]August[/name] is more popular right now but strong enough and old enough to hold its own with [name]Charles[/name]. [name]Charles[/name] and [name]August[/name].
[name]Arthur[/name], gold-standard classic male name. I would probably call him [name]Archie[/name] for short, though, rather than [name]Art[/name]. [name]Charles[/name] and [name]Arthur[/name].
[name]Ambrose[/name]. Okay, I’m biased, its the name of a favourite author of mine, but [name]Charles[/name] and [name]Ambrose[/name] sound very distinquished.
[name]Amos[/name] - underused Biblical name that isn’t difficult to say or deal with. I really love [name]Amos[/name] and don’t know why [name]Aaron[/name] is comparatively very well-used and [name]Asher[/name] is trending up, but [name]Amos[/name] languishes. [name]Charles[/name] and [name]Amos[/name].