Who is Ingvi-Frey?

Ingvi Frey was known as the Lord of the Swedes. The Icelandic chief and author of the Eddas, Snorri Sturlusson wrote that Ingvi-Frey had lived at Uppsala. He was associated with sacral kingship and divine blood, he founded the Yngling dynasty. 

The 11th century German chronicler, Adam of Bremen also wrote of the importance of Uppsala to the pagans. He said that the temple there was covered in gold and that it contained statues of Odin, Thor and Ingvi-Frey

I believe Frey and the other Vanir gods represent the remnants of a pre-Indo-European religion which was integrated with the Indo-European religion to form the Germanic pagan tradition in the Bronze age.