First cousin twice removed

Here the two people sit two generations apart. One is a grandchild of the shared couple; the other is a great-great-grandchild. So your grandfather's first cousin is your first cousin twice removed, and you are his.

The rare word grandcousin has been used for the same relationship. In old records this person is usually just called cousin, and the gap in ages may be large. If a will names a cousin who was born two generations before the writer, this is one link worth testing.