I had posted something about this a looooong time ago--I can't even remember the thread now! I think that there were hopes of a match between Elena and Nicholas but I can't remember if it was on her parents' part, his or both. She was attractive, good-natured and Orthodox so it seemed a good idea. She certainly made a wonderful Queen of Italy--though the Kaiser mocked the height descrepancy between her and Victor Emmanuel.
Here's the whole family (with in-laws):

Back Row: Grand Duke Peter of Russia (married to Militza), Prince Franz Josef (Franzjos) of Battenberg (married to Princess Anna), Princess Vera (?) and Grand Duchess Stana (?), Crown Prince Danilo (?), Prince Mirko (?), Prince Peter (?)
Middle Row: Crown Princess Militza (nee Jutta of Mecklenberg-Strelitz), Princess Xenia (?), Princess Anna, Queen Milena, King Nicholas, Grand Duchess Militza (?), King Victor Emmanuel of Italy, Queen Elena of Italy
Front: Princess Helen of Serbia (dau of Princess Zorka), Princess Xenia (?), Prince Alexander of Serbia (later Alexander I of Yugoslavia—the potential suitor of Grand Duchess Olga)
Their eldest daughter Zorka who’d married the future Peter I of Serbia had died in 1890. The children in order of birth (so many girls in similar ages and appearances is why I’m not 100% sure of some of the above IDs). I’ll put the names in chronological order so people can compare and make up own mind:
1. Zorka m. Peter I of Serbia (though she died before he became King)
2. Militza m. Grand Duke Peter of Russia
3. Stana (Anastasia) m. (1) Duke George of Leuchtenberg div. 1906; m (2) Grand Duke Nicholas of Russia (brother of Peter)
4. Marija d. 1885
5. Danilo (abdicated in 1921 in favor of nephew Alexander becoming King of a united Montenego and Serbia as Yugoslavia) m. Jutta of Mecklenberg-Strelitz who took name of Militza
6. Jelena (Elena) m. Victor Emmanuel II of Italy
7. Anna m. Prince Francis Josef of Battenberg (brother of Louis, Alexander and Henry)
8. Sophie d.1876
9. Mirko
10. Xenia
11. Vera
12. Peter