"Anam Cara" is a shorthand that seems to have been reinvented for contemporary use by the Irish poet and author, John O'Donohue. He translates it to mean "soul friend" which would be a rough approximation of the special connection between two like-minded people alluded to in the word "simpatico".

Here is the Amazon.com website for the book "Anam Cara: A Book of Celtic Wisdom" by O'Donohue:

http://www.amazon.com/exec/obidos/tg/detail/-/006092943X/002-3434247-8488059?vi=glance

Not being a native Irish speaker, I wouldn't really know if there is an equivalent to simpatico. There often aren't (pardon my pun) sympathetic words when moving from one language to another.