There are no direct descendants. These children died before being married or having any off-spring. If you are related to the Romanov family, then it is only possible through the relatives of the last Tsar or Tsarina. If you claim to be a descendant of any of the last Imperial children, then you have to forgive me but I cannot believe you.
Oh, that sounds interesting! May I ask his surname? I could perhaps find some info on him. In any case while that makes you a descendant of a Russian aristocratic family, but not a relative of the Imperial family.