What do you mean by "combine"? Please explain your problem in lots of detail. Lots and lots and lots of detail.
Also, please make sure you state your version NUMBER of Lightroom (do not state that it is the latest version or that Lightroom is up to date).
Do you mean View both JPG and RAW file after you import from a cameras memory card? There is a setting in the LR preferences to treat JPGs next to RAW files as separate photos. It is on the General tab of the preferences. By default that option is not checked.
If that is not your problem then we will need Lots and Lots and Lots more info on what you mean by Combine