There’s a great history of harmonizing brother duos, from the Everlys to the Williams Brothers. Jonathan McEuen and Jaime Hanna would qualify on Hanna-McEuen. . .if they were siblings. But they’re cousins, born to twin sisters and Nitty Gritty Dirt Band dads — and that’s close enough. Country’s had a strong Southern accent lately, but anyone seeking a smoother, lonesomer, less geographically defined throwback to, say, the Mavericks will find this bow a euphonic, often euphoric alternative.