As a world-famous occultist, Mme. Blavatsky needs no introduction. Even in death, her influence continues to play a role in modern beliefs, and can be seen across the Internet.
That said, Blavatsky has an interesting background, and channeled her family's genealogy at the request of her father, Col. Peter Hahn.
Hahn was of noble stock, and related to the Mecklenburgs, while Blavatsky's mother -- a descendant of Grand Duke Rurik -- was the daughter of Princess Helene Dolgorouky. Her name was also Helena, and she gave birth to HPB on a late night between the 30th and the 31st of July. Although this date correlates with the Julian calendar, it's steeped in folklore and was of special significance to the locals. So special, that according to her family, Blavatsky was dubbed "Sedmitchka" by local serfs.
The date in question offered the future New Ager protection from a normally benign "Domovoy" (house goblin), that became a trickster every March 30th. Only those who share Blavatsky's birthday are offered protection.
Ironically, family history states that things didn't work out so well at HPB's Russian Orthodox baptism. Her aunt, just a toddler at the time, accidentally set the priest's robes on fire and the poor guy suffered severe burns. The town thought it was a bad omen, but as things turned out... Blavatsky became a legend.
Father: Col. Peter Alexeyevich von Hahn, son of Countess Elizabeth Maksimovna von Probsen and Gen. Alexis Hahn von Rottenstern Hahn
Mother: Helene Fadeef, dau. of Privy Counselor Andrew Fadeef and Princess Helene Dolgorouky  or Helena Andreyevna Fadeyev (11/23 Jan 1814 Kiev - 1842)
m.1 Nicephore Blavatsky 07 July 1848. Separated.
m.2 (03 Apr 1875 - 25 May 1878 divorced) Michael C. Betanelly .