1) even though it won't cause a compile error, using LINQ, or any other reserved name, that is identical (except for character casing) for a MS defined term is a very bad practice: it may make your code seem ambiguous.
2) you don't do anything with 'doubleFamilies.
3) if you can find 'e, finding 'ee is just a matter of your studying string.Contains: [
^]; look at the overloads.