There are two ways to go about accomplishing this - in camera and in post.
Both techniques will rely on shooting a rim-lit subject.
Put a flash behind the subject. In my image, I actually had the flash cranked up WAY too much, so I'm getting additional light acting as fill (bouncing off the couch and back toward the front of the subject):
Set-up below shot is below. Flash is a 430EX set to 105mm, full power, with 3 MagMod grids attached. They limit the light to 15 degree beam. I'm shooting directly opposite the flash, putting Yoshi right between me and the flash.
And the resultant image:
Technique 1: post pro add in
Now, some rough clean up work to darken everything around my couple:
And finally, topping with some stock bokeh shot. Bokeh meshed using Add method and slightly less opacity. Bokeh used from https://www.pexels.com/photo/time-lapse-photo-of-lights-220118/ under CC license.
Assuming you take the time to do this right, I'm sure you could do a lot better. But, to recap:
- Have a point light source firing from behind, this is called a rim light
- Darken any areas that you want gone in post
- Add a stock bokeh shot on top, whether yours or purchased. (Creating your own stock bokeh photos is simple and fun. All you really need are some Christmas lights. Here's a good how-to)
Technique 2: in camera
And here's the shot redone holding this string light in front of the lens. It's a bit bright where I am right now and I didn't darken out the BG. Please excuse that for this example...
Photo of the lights:
Photo of the shot:
Having a big handful of Christmas lights would be better than this simple string. Also, it's terribly hard to use string lights when a cat is in the room.
To restate: These are two very different techniques to accomplishing the same thing. Many photographers are in-camera purists and will despise the above technique. If you have the time, by all means, go for in-camera. If you are shooting this on location with a non-model couple, then I would advise getting a shot without the foreground bokeh...just in case you need it later, because, now you know, you can do this technique in post quite easily.