Going to use a couple tenor singers from some all time great country quartets as examples.
Jimmy Fortune from the Statler Brothers has some great high range for a male singer. Using a video of him as a solo artist as I love the harmonies in this version. The gal is Sydni Perry who is currently Carrie Underwood's backup singer
Joe Bonsall for the Oak Ridge Boys can really get up there too. Probably some better examples of his range when he's singing the high harmony parts but this is probably my favorite ballad he sings lead on
I'll throw 1 more in the mix while I am at it, Jamie Dailey from Dailey & Vincent can hit some high notes as well.