The UY is the deciding factor; home resorts can be different. As long as you have the same UY and have titled the second contract exactly the same as the first, down to middle initials, you will see the new contract show up under your original member number.
The two contracts will be numbered something like this..
FIRST contract - 12345.000
SECOND contract - 12345.001
You will see them like that when you log into your
DVC account.