Each of them managed to marry a real wife at least once.
P.S. Read "Wonderful Tonight" by Patti Boyd and you will be grievously disappointed at how a woman who had multiple songs written about her by two musical greats could possibly be so boring. I'm not even going to bother with the sequel.
Read "John" by Cynthia Powell Lennon (etc., etc.) and you will not only enjoy a definitive John Lennon biography, you will have your "mousey little first wife" misapprehensions destroyed forevermore, making the "why" of Yoko all the more mystifying.