Mark is good.
Try and watch him [ or Kathy Mattea] sing 'Mary did you Know'.
Yes, great voices both of them. My four girls used to gather around the piano, either #3 would play or her eldest daughter would, and that was one of the songs they used to do. Now that two are gone, the other two refuse to sing any more, breaks my heart but oh the memories are precious. If you want to hear another beautiful duet, this one on Youtube "Knowing What I Know About Heaven" with Guy Penrod and Sarah Darling.
https://www.youtube.com/watch?v=yduN-IC7bOA