Can two mediums placed under same conditions* ever have same refractive indices? *Pressure, temperature,etc.
yes, enantiomers (compounds the molecules of which are mirror images of each other, but not identical) have the same refractive index.
Also, if the question is not limited to pure compounds, two miscible compounds could be mixed to match the refractive index of a third compound to an arbitraily close degree.
While these are at the same temperature and pressure, they're not in the same state, so I'm not sure if you'd be satisfied: glycerin and glass have the same (or at least extremely similar) refractive indices in everyday conditions, which leads to some neat optical effects where glass seems to disappear.