There was a book I used to read all the time when I was a kid. I literally paid so much in library fines I should have just kept the stinking book–I probably paid for it two or three times over!
It was set in Scotland, had two brothers, one named Ian. There was a girl who had the second sight, and her name was Kelpie I think. She was in love with the other brother–not Ian–and Ian totally mistrusted her. From my 12-year-old perspective, it was a very intense book.
I’ve googled it and searched at alibris.com and haven’t found anything. So I turned to my fellow dopers, who have yet to let me down! 
I did a quick Amazon search for “Kelpie” in children’s books. Any of these sound familiar?
“Quest for Kelpie” by Frances Hendry
“The Lothian Run” by Mollie Hunter (there seems to be a whole “Kelpie” series for children)
I don’t think either of those are the ones. It would have been around 1974-75 or so when I was re-reading it constantly. These look newer. I’m not giving up–just hoping someone else had run across the same book.
Thanks for your help!
The Lothian Run was published in 1970, FWIW.
The Lothian Run,
by Maureen Mollie Hunter McIlwraith (Hardcover - June 1970)
Out of Print–Limited Availability
Again, thank you–I looked that one up, and that’s not it either. You guys are awesome for helping!;j