sorry i got a bit mixed up with your post!!
the statement for the refusal is not clear....
they are not convinced that i will have my vacation in UK 8 months before my wedding..
....why would they refuse you to come for a family visit visa if you just intend to visit your sister???
is your fiance also lives here in UK??
what is stated in your certificate of employment?
is your employer happy to employ you back after your visit visa to the uk?