most pepper species cross prolifically with each other.

Unless you're talking indoors where there is no wind, no bees, and they are perhaps far enough apart that pollen won't travel from one to the other, then cross-pollination is a very real possibility.

Oh, and plants don't care what their name is :) they just want to reproduce.

For peppers not to cross they need to be 500 feet apart or incompatible. Here is a chart.

Easiest way to prevent crossing is to isolate branches or plants with tulle which you can buy cheaply at Wal*Mart

If you are not planning on saving seeds from the crops, then don't worry bout crossing. Crossing will not affect the fruit this season, but if you use the seeds saved from the crop next year, then you may have a suprise when biting into that "sweet pepper".

Here is a link that might be useful: My Pepper Garden