Do they have the same Shipset name in their details? If so, tough luck. If not, you could create two silly ships for them, or something to that effect.
I actually play with few shipsets, so most ships look pretty much the same for me, but I wouldn't advise doing that if you like your game display clear and efficient.
(I *know* where your ships are, so I don't rely on a graphical display for them)