Not quite sure what the context of this is - collecting C & H names?
In any case, I don’t think Cathal is an immediately clear match to your others that are more familiar (across English speaking countries etc). But it could be - obviously in Ireland it might be. Meanwhile, I would have offered Christopher (nn Kit) - it would go so well - as a counterpart to the equally classic Caroline but it’s not what you’re looking for (even with Kit as a nn?).
How about:
Callahan
Calloway
Curtis
Conall
Cecil
Clement
Chester
Claude
Cormac
Casper
Camden
Charlie
Conrad
Some aren’t “old fashioned” (in the well-known sense) but they go with Hazel and Caroline for eg.
I really like [name_m]Cathal[/name_m], though I agree its maybe not a perfect fit with your set. [name_u]Love[/name_u] the previous suggestions of [name_m]Conrad[/name_m] and [name_m]Cormac[/name_m]!
I don’t personally love [name_m]Cathal[/name_m] with your options. Where I live (US), [name_u]Hazel[/name_u], [name_f]Caroline[/name_f], and [name_u]Henry[/name_u] are all fairly common names, but I have never heard of [name_m]Cathal[/name_m] before, which is why it doesn’t fit as nicely, in my opinion, but that may be different in [name_u]Ireland[/name_u]!
[name_m]Colm[/name_m], [name_m]Cormac[/name_m], [name_m]Crispin[/name_m], and [name_m]Caradoc[/name_m] are all favorite C names of mine.
[name_m]Cathal[/name_m] is a terrific name (and the name of a wonderful character in [name_f]Elly[/name_f] Griffiths’s [name_f]Ruth[/name_f] [name_m]Galloway[/name_m] novels).
Hmm, how about:
[name_u]Charles[/name_u]
[name_m]Crispin[/name_m]
[name_u]Clayton[/name_u]
[name_m]Connell[/name_m]
[name_m]Cullen[/name_m]
[name_m]Cuthbert[/name_m]
[name_u]Corbin[/name_u]
[name_m]Conrad[/name_m]
[name_u]Curtis[/name_u]
[name_u]Claude[/name_u]
[name_m]Cormac[/name_m]
[name_m]Cillian[/name_m]
[name_u]Callum[/name_u]
[name_u]Carlisle[/name_u]
[name_u]Clyde[/name_u]
[name_m]Clint[/name_m]
[name_u]Clovis[/name_u]
[name_u]Corrin[/name_u]
[name_u]Clare[/name_u] ton or [name_m]Carleton[/name_m]
[name_m]Cap[/name_m]
[name_m]Caspar[/name_m]
I like [name_m]Cathal[/name_m]! That’s very cool. It works with your other choices to me, even though it is more distinct. They all seem very storybookish and exciting.