I know it's possible to create multiple FK's to different tables using the same column, other than the performance hit caused by having a FK, are there any negative consequences of doing so?
http://sqlfiddle.com/#!3/afb95
CREATE TABLE A (aid int primary key);
CREATE TABLE B (bid int, aid int null);
CREATE UNIQUE NONCLUSTERED INDEX [BIdx_aid] ON [dbo].[B] ( aid ASC) ;
ALTER TABLE b ADD CONSTRAINT FK__B__aid__A__aid FOREIGN KEY (aid) REFERENCES A(aid);
CREATE TABLE C (cid int, aid int null);
ALTER TABLE c ADD CONSTRAINT FK__C__aid__A__aid FOREIGN KEY (aid) REFERENCES A(aid);
ALTER TABLE c ADD CONSTRAINT FK__C__aid__B__aid FOREIGN KEY (aid) REFERENCES B(aid);