In genealogy, what is an "island" tree?

Question:

In genealogy, what is an "island" tree?

Someone wrote to me that he has an "island" tree, so his connection to many of them is "merely collateral". What is he saying?

Best Answer - Chosen by Asker: It may be a family tree of someone who is a relative, but not a direct ancestor. A collateral relative is a brother or sister of an ancestor. His is saying the tree that he has does not have a direct path to himself.