Russia - Passport & Nationality - Russian Citizenship by Descent
If both parents are citizens of the Russian Federation, their child shall be a citizen of the Russian Federation irrespective of the child's place of birth. If one parent is a citizen of the Russian Federation and the other is of another citizenship, the child's citizenship shall be decided, irrespective of the child's place of birth, by a written agreement between the parents. (In the absence of such agreement, the child shall acquire citizenship of the Russian Federation if it were born on the territory of the Russian Federation or if it would otherwise become a stateless person.)