Who or what is this poem referring to?

 

>Within me you will find<br>
One of like heart and mind.<br>
As well as an entity<br>
With inverted geography.

>While I represent symmetry<br>
Mirrors can show another identity.<br>
But there will always be twins<br>
Who generate many grins.<br>

Hints:
>! The first 4 lines and last 4 lines should be interpreted differently.  Also, avigrail's [comment][1] about boobs is somewhat related to the answer.


  [1]: https://puzzling.stackexchange.com/questions/6122/riddle-poem-within-me-you-will-find#comment19706_6122