It has been suggested that Glorfindel is somehow related to Finarfin, although he does not appear in the family tree of the House of Finarfin and it is said by Tolkien that Finarfin and his descendants alone among Noldorin princes had golden hair.   The likeliest explanation for this statement is that at the time Tolkien had not fully worked out the kinks of Noldorin genetics, as one of Fëanor’s sons, Celegorm the Fair, was undoubtedly golden-haired.

Several individuals, including Michael Martinez, author of Visualizing Middle-earth, have speculated that Glorfindel was the product of the marriage between a Noldorin lord and Vanyarin lady.  Martinez also suggests that Glorfindel “probably could not have been an "elder" among the Noldor at the time of the rebellion,” as very few of the elder Noldor, such as Nerdanel and Mahtan, went into exile.

In Tolkien’s essay on Glorfindel, in The Peoples of Middle-earth, it is suggested that Glorfindel was an adult at the time of the rebellion of the Noldor and followed his people reluctantly.  However, this version is not set in stone as Tolkien himself did not publish this essay and I have chosen to make Glorfindel a child at the time of the Noldorin rebellion.  This is still in accordance with the reference from The Lord of the Rings that he is an Elda of Valinor, while absolving him of the guilt of the rebellion. 

Nowhere does Tolkien say that Turgon sent emissaries abroad from Gondolin, but as he does mention that Turgon closed the Hidden Way after the Nirnaeth Arnoediad and allowed no one to travel to or from the vale of Tumladen after that time, and given that Fingolfin was Turgon’s father as well as his High King, it is reasonable to assume there must have been some carefully guarded traffic from Gondolin before the Unnumbered Tears.