SK127510 JUL 2018 : 9 posts by 4 authors. Attachments (6)- around 600 kb each. 

Location:  Kalimpong, WB, India
Date: 10 May 2018
Altitude: 4600 ft.
Habit : Cultivated
Begonia …… ???

Most probably Begonia cultivar

Yes it is Begonia cucullata. Perpetual begonia

Does not match description in this PDF of Begonia cucullata, which is  classified as an invasive weed in USA.


from page at univ fl

read the pdf particularly  flowers description and that of the leaf.
these things are taught at community levels in USA to identify the invasive species and to help eradicate them.
The begonia you are showing is NOT the invasive begonia cuculata flowers, leaves shape tip base etc do not match the description.
This is but one such circular.
i believe Australia has such papers also.
I have never seen violet or reddish leaves on the weedy begonias.
your plant is a cultivar of double begonias, with thousands of them its beyond me to classify them.
but its not the invasive species. this one is  an exotic houseplant.

Something like Begonia Rose

classifying begonias is like pulling teeth based on pictures of a potted plant.
any of the showy many petalled begonias are ultimately derived from tuberous begonias.  
many call them Begonia tuberhybrida oerall, flowers of which can be many colors and each nursery or breeder then names his or her variety 
and may be gets them registered.
this link that Gargji gave is one such but their leaves are green, pointed, seem thinnish, not the beefy looking brown in this case here
and leaves are shiny. to be sure one will have to find the hybrid maker. but to guess on a name
i would stay with Double begonia cultivar rose pink or some such name
USDA plants site seems to be down for sometime now otherwise we could have had a better idea