Vikki,
Are you still out there? I just came across this post and have a couple questions. Are you saying that your McElwaine's and Johnston/e's were from County Cavan, Ireland? I have McElwaine's from there and know someone whose family includes BOTH McElwaine's and Johnston/e's from there. Post back if you're still around, or email me at my personal email - walterskk@hotmail.com - if you think we might be able to help each other. Thanks!