If the old FP is going to be in a separate room, it will probably be ok. In other words, are you going to define the space around the old FP as something other than the family room (breakfast nook/keeping room) it should be fine. It's your house, so if you like it, go for it!

Thank you and good point. They are both in the same room, however the ceiling will be a divided tray - meaning a separate tray for the couch family and a separate tray area for the dining area also close to a large archway entering to the kitchen. In other words, the fireplaces are both in
one room, however the dining and couch areas will be somewhat defined by two large area rugs and two defined tray ceiling in the same large room. Hope this makes more sense.

You wouldn't have to use both at the same time, however, in an extreme cold snap, might come in handy to get them both going at once. I wouldn't drywall it up even if you didn't use it.

On our build, we have a gas fireplace. We plan on an addition just off that room where we will have a woodburner which will become our main heat source. With a wood burner in our area, you are required to have a gas fireplace or furnace back up. They wont be in the same room like your situation, but will be close. Efficiency as well as asthetic wise I think it's going to be a good idea!

I have two fireplaces on each side of my room. It looks great and though some may think that's odd- I like it- and if you like it in your home- do it!

Helpful advice if it had been given 4 years ago.