I'd go with Callan or Callen. I would think that Calan was pronounced CaLAN. Callin just looks like 'calling' without the 'g'. I would assume Calin was a girls' name and would pronounce it Caylin. Ditto with Calen. It's a handsome name and goes well with Brendan, but they are going to have to deal with spelling and pronunciation issues.

I'd go with Callan. When I read the title of your post, I read it like KAL-an. Most of the others I'd pronounce differently.

Okay, this is how I'd pronounce them...

Callan and Callen = KAL-in, their desired pronunciation. Unfortunately for the dad, the double consonant following the "a" signals to me to use their desired "short" vowel (eg. tapped vs. taped; supper vs. super)

Callin = While I would normally say this as KAL-in, use of this word as a shortened form of "calling" makes me say it KOL-in. However, I could easily learn to say this as KAL-in

Calan, Calin, and Calen = I'd instinctively call all of these KAY-lin due to the single consonant. (I also don't particularly like how Calan looks, but that's neither here nor there.)

The only one I really want to pronounce Kay-lin is the Calen spelling. The rest are Kal-in to me. But I think the Callan spelling works best with the pronounciation. If they really don't want double Ls then I don't think Calan would be a problem (and they can always say it rhymes with Alan if people are confused).

I agree with what Karyn posted above. The double L is what signals the pronunciation they want—with a single L it's much more ambiguous (with Calan in particular, I might think it was a Spanish name, pronounced cah-LAN). I would personally choose Callan—I don't know whether this or Callen is the more traditional spelling, since as far as I can tell these are both Anglicizations of an Irish spelling anyway, but the -an spelling *looks* more like an Irish name to me (the -en makes it look more like a random surname choice or a made-up name). Callin just looks like a mis-spelled Colin. 

I agree with everyone else: Callan is the clear winner of the versions you've listed. In general, the name fits in with current trends (perhaps a little too well) but is also unfamiliar, so they are likely to end up having to clarify a lot, and having the most intuitive spelling will really help.

The single-L spellings make me want to guess either that the name is another rhymes-with-Jaylen variant or perhaps (especially since it is unfamiliar) that it is a foreign name where the vowels are probably pronounced in the same way (or similarly to) Spanish/Hindi/Japanese/pretty much most other foreign languages, which don't contain the a-as-in-apple sound they're looking for. I.e. I'd read a as "ah," like the a in father, and additionally, I'd second-guess the syllabic emphasis and pronouncing the second vowel as a schwa, to potentially end up with Calan = KAH-lahn or kah-LAHN, Calen = KAH-lehn or kah-LEHN, Calin = KAH-leen or kah-LEEN.

Of the double-L spellings, Callin makes me think of "calling" without the g, and Callen I'm torn between pronouncing the same or rhymes-with-Allan. Only Callan makes me automatically go for the pronunciation they want, although I could still imagine this spelling being pronounced KAH-luhn and expect they would still encounter that version occasionally.

I also agree that Callan with the -an ending "looks" the most Irish, especially next to brother Brendan's name, which might be a useful cue. Perhaps because of this, it also reminds me of Callum, which I recognize as Irish (and really like - any chance they'd just go for this?), way more than the other spellings do. Incidentally, I know Callum means "dove" - is anyone here familiar with Callan?

Hope this is useful.

Callan, I think, is best, if your aiming for a spot-on pronouncation. As much as the father may not like the double-l, it enforces the spelling they want, and if that's important to them, they might want to go with that. At the same time, people (such as classmates, teachers & other friends) will get used to unusual spellings easily, and read them as you want without fault very quickly. Trust me, I know people who've had that very problem, and it's worked out fine in the end for them. Go with what you like most, a mispronounciation is usually only interpreted by classmates as an inside joke, and source of some good-natured kidding by friends -no harm done in that. :)

Your friend may have had her baby by now, but I just wanted to say that I know someone with a (10?) year old Callan, spelt that way and pronounced KAL-in.  I prefer Callan of all the options with Callen as a second best.

I vote Callan too- the way they want it pronounced is how I read it in my mind first off.

Hey everyone, just wanted to say a big thanks for all your great advice!  I sent this thread to my friend (and her husband) and they decided to go with the Callan spelling :)

Callan Michael was born this past Saturday.  Mom and baby are healthy and happy!

Thanks again!

Our son is named Calan and the pronuciation is with the short "a" not Long; names do not follow traditon english langauge rules. The name is both Irish and Scotish meaning contemporary child