Re: Installing SONY GPS unit ... want to wire it in directly
You could crimp them both into the same connector but you'd be "sharing" a fuse. If one or the other device develops a problem and blows the fuse, you would have a little extra work figuring out which. And if for some reason their combined power requirement exceeds the fuse rating, you might blow fuses. Putting a "20a" fuse in to handle two 10a units would be bad because the fuse wouldn't blow if one of the units had a problem until it was too late. Better one fuse per device, but it will "work" if you wanted to test it once.
Ground both yes, and they can touch. I have a ground terminal that I made for all the stuff I added and it's all on one stud.
I used a piggy back fuse connector in the underhood fuse box to keep it all clean, and concentrate the fuses in one place. I didn't want to cut into any wires and this approach allowed me not to.