Melody Pond was the child of Amy Pond and Rory Williams. She was a "child of the TARDIS", born mostly Human with some Time Lord DNA. She was transformed by the Silence into the first of several Proto-Time Lords, and had the ability to regenerate.
Melody was named after her parents' childhood friend, Mels Zucker, who was in fact secretly her second incarnation gone back in time to ensure her parents got together. Regenerating once more into her third incarnation after being shot by Adolf Hitler, she became best known as Professor River Song, and married the Time Lord known as the Doctor in his eleventh incarnation.
Biography
Incarnations of Melody Pond
During her first incarnation, Melody was a little girl, who had been kidnapped by Madame Kovarian. She harvested Melody's embryonic DNA in order to clone more children like her. This resulted in the creation of River's clones, the Proto-Time Lords. The clones referred to one another as siblings. The first batch consisted of seven clones named Lake, Rindle, Tarn, Wadi, Creek, Stream, and Beck. (AUDIO: The Lady in the Lake) The second batch of clones included Brooke, H-One, H-Two, and O. (AUDIO: My Dinner with Andrew, The Furies) Like River, the clones had two hearts and the ability to regenerate; however, the exact amount of regenerations each of them had was random. (AUDIO: The Lady in the Lake)
After escaping from the Silence, Melody had made her way to New York City and developed a terminal illness, but knew she could "fix it" by regenerating. She was living homeless in an alley when she finally succumbed to her ailment in January 1970, and regenerated. (TV: Day of the Moon)
Now under the name of Mels Zucker (PROSE: Mels at School) and residing in Leadworth, Melody grew up once more, now alongside her parents. She became Amelia and Rory's close childhood friend, (TV: Let's Kill Hitler) Upon meeting the Eleventh Doctor, Mels held him at gunpoint and made him take her to "kill Hitler". There, she was caught in a crossfire between him and the Teselecta. She got the Doctor to promise to marry her, and revealed her true identity to the three of them. Beginning to regenerate, Melody reflected on her last regeneration, and told her parents she was glad she had found them, before she exploded with regeneration energy.
Shortly after regenerating, Melody began examining her new body. Unbeknownst to her, both the Doctor and her parents were already acquainted with this new incarnation, who more commonly used the name River Song. (TV: Let's Kill Hitler)