How can two people be so different yet so alike?

[biteme]

How can two people be so different yet so alike? I really want to know the answer to this one...I even went as far as asking a person I didn't even know...

[iwbym]

my ex who wants to get back with me...did a test...she said her ex and I are exactly alike yet...we're different in how we treat her...also we're different in our physical appearance (and "size" as well)...i happen to treat her with respect and except for one wrong thing I did I haven't hurt her yet...plus I haven't lied to her...yet while her boyfriend has the same personality as me same interests etc...he treats her like crap...lied to her...cheated on her...and hurt her one too many times

hope this helps