<h1 class="subject">Is there any device that combines water from 2 different faucets (hot and cold) to give just one water stream?</h1>

I hate how the 2 faucets are placed apart and I only get either very hot or very cold water, not warm water.

At appliance supply or plumbing stores you can buy an appliance hose that looks like a "Y". Each leg connects to the hot and cold tap then you can connect something else to the leg of the "Y".

With all due respect I'd give the 10 to # 1.

What it will mean is replacing the existing fixture, even taking it a supllier, so that the inlets that center in the sinks holes/openings, can be matched.

Certainly if not an entire new fixture the plumbing can be managed under the fixture to MIX both hot and cold. The plumbing you have/mention, has to be archaic in any case.

Double inlet/ to single flow taps, are as common as flowers in the last few decades.

Just my two "sense"

There is a Y connector for threaded faucets that is used to adjust temps for portable washers.

If you want it permanent, you can shop for faucets that will go through a single hole (you plug the other one) and connect with the two lines below or that fit through both holes if the spacing is right. They have a single handle that goes left right for hot cold and either up and down or fore and aft for volume. Delta is one brand. http://www.deltafaucet.com/wps/portal/deltacom/Style

assuming you are talking about something like a service sink that has two separate spouts

could buy a new combination faucet with inlet spacing to match your sink or

you could possibly buy two elbows that would fit the existing aerator threads on faucets and run short pipe from each to a T in the middle

have seen commercial faucet that looked like that so they may even make a kit

called a mixing valve most modern sinks have them what vintage sink do you have there

a mixer tap

Go to Home Depot or Lowes and ask them. They would know exactly what you need.