Celtic Thunder and Relient K

The current band I'm obsessing over is Relient K. Wait...make that two bands: Relient K and Celtic Thunder.
They're two very, very different bands. However, I'll only talk about Celtic Thunder because I haven't actually done much research on Relient K. I'll post some videos from each sometime soon.
~ ~ ~
Celtic Thunder is a five-man band (although they sometimes have someone else sing a song or two, or do background vocals).
They change members quite often, but the five who were on the band for the longest (and still do special concerts together sometimes) are as follow:

George Donaldson
Paul Byrom
Ryan Kelly
Keith Harkin
Damian McGinty

They all have specific styles of singing. As far as I can tell, George Donaldson tends to do the more traditional Irish singing style. He's the oldest member of the band.
Paul Byrom would make a good opera singer; he has a really deep (some have used the term 'velvety', though I don't use that word often, XP) tenor voice. He's the next oldest (although Ryan Kelly is the same age).
Ryan Kelly seems to like to sing the 'bad guy' songs, where he plays the rogues. For instance, he's sung songs where he's the Gypsy King, a ladies' man...basically, he likes to sing songs like that. He's the only member of the band (as far as I know) that's published his own album.
Keith Harkin has a country-boy way of singing. I dunno; it reminds me of a guy singing folk songs. Probably because those are what he sings.
Damian McGinty is the youngest of the team. And it's hard to take him seriously, because he looks so young in most of the YouTube videos. XD When he was younger, he had a young voice, obviously. Now that he's older, his voice is a lot deeper, almost like Paul's, but not quite. He tends to sing love songs or songs about teenagers.

I'll include some videos of theirs later (a solo video for each of them, and one or two ensemble videos).
The thing that I was most drawn to is that all of them are Irish. You can't hear their accents very well when they sing, but in their interviews...wow. They've got some very unique accents. Or I suppose they would be called 'brogues', since it's Irish? I'm not quite sure about that.
Some of my favorite songs of theirs are "Stand and Deliver", "Ride On", "Happy Birthday, Sweet Sixteen", "Outside Looking In", "Ireland's Call", and "Heartland".