Aug 9 (Reuters) - A Kremlin official involved in what international prosecutors call the illegal deportation of Ukrainian children to Russia was associated online as a teenager with white supremacist and neo-Nazi movements, Reuters has found. The material posted online by Alexei Petrov between 2011 and 2014 remained on his social media account until late July this year when, following questions posed by Reuters, he deleted some videos, unsubscribed from two far-right online groups, and made one of his accounts private. A photograph of Alexei Petrov, advisor to the Russian presidential children’s right commissioner, taken from his profile on the...