Disclaimer: I Do Not Own Doctor Who.
They were closer than anything once, but that was so long ago that planets and galaxies had turned to nothingness and became a part of legends.
There they were two lonely children, unlike everyone else around them not outwardly different, but the things they thought and the way they acted was different.
One dreamed of running forever and seeing a million different worlds while the other dreamt of destruction.
Both of their dreams poisoning their friendship until the only thing that mattered was who would was winning.