If the two Reubens are owned by the same entity, the sensible thing to do would be to call them Reubens 1 and Reubens 2. Which reminds me of the Springfield, Mass. strip club Mardi Gras, which is technically Mardi Gras 1 although not so named, because the owners opened a satellite club across the border in Ellington, CT called Mardi Gras 2. I was in Mardi Gras 2 a couple months ago and it sucked. I heard the other Mardi Gras is good/better if any of you are ever in Springfield.
If the two Reubens are not connected, then one is infringing on the trade name of the other and a lawsuit might be appropriate to avoid confusion of the consumers. Trade name rights are usually determined by who was using and properly registering the trade name first, under applicable local laws.