If two Hominin met...

Humans today have never interacted with another species of hominin because we are the only species of hominin still alive... for now. This is not usually the case. In the past there is evidence of more than one hominin species living at the same time. We also have confirmed that not just at the same time but in the same area!!! And in a unique case even in the same cave in Drimolen, South Africa!!!! 

So what would it be like for two species of hominin to meet? There is no way of completely knowing to my guess is as good as yours. Given the nature of life and survival of the fittest and all that one can assume how things went down. I assume that when two species of hominin first came across eachother the first thought was fear of the unknown. They probably thought something along the lines of "they look kinda like us but they're not us so they must be a threat". They also probably thought the other was invading their territory. So the first interaction may have been hostile or defensive. Now if they could get past the fear of each-other and learn to coexist (as we know some have) then I believe there would have been a lot of competition. Competition for mates between the species, competition for food, and competition for territory. I bet even a Romeo and Juliet scenario isn't completely out of the question