Well this is based on what both Dan and Emma have told the press and that is "No." They have had no kind of relationship other than A brother/Sister type one. Now all opinions are diffrent some people think that they are in love but others just find it diffrent. :)
I saw interviews with Emma where she spoke of the awkwardness of doing kissing scenes with both Dan and Rupert where she referred to them as friends. Emma was quite competitive when they were doing the snatcher chase scenes through the woods in the Deathly Hallows Part 1. She seems to be a very well-grounded young woman. As Dan has turned 22 in the summer of 2011, Emma must be about 23.