IngIng is first mentioned in Pliny's history and Tacitus' Germania as progenitor of the tribal grouping Ingvaeones, and a son of Mannus. He is mentioned in the Anglo-Saxon Rune Poem:
Ing was first---among the East Danes
Seen by men---but he since went eft (back)
Over the wet way---his wain (wagon) ran after
Thus the Heardings---named the hero.
Ing is found in several Old English compind names such as Ingwine, "friend of Ing." An Ingui is named in ropyal the geneanology of the Anglo-Saxon of Bernicia. Even though he is fairly far down in the list, it may be that he was the real founder of the line, and the precedding generations were added later when it became popular to trace one's line to Woden. Ingibrand appears in some versions of the line while Inguec appears in others.
Frea (Freyr) is known as Yngvi Freyr ancestor of the Swedish royal line. It is therefore commonly accepted that either Ing and Frea are one and the same, or that there was a hero Ing and a God Ing i.e. Frea. There are several problems with this. Ing is shown in Germania as a deity, and his link to a wain in the Old English rune poem would seem to indicate this. Grimm theorizes that Bor is Mannus, and therefore Irmin is Odin while Ing and Istaev would be Villi and Ve. This is a possibility of course, but then again may be as unlikely as Ing as Frea. If one accepts however, that Nörðr as Frea or Freyr's father was an invention of Snorri, one can accept Ing and Frea as the same. The only place outside of the Heimskringla and the Prose Edda Nörðr is mentioned as Freyr's father is the Lokasenna, a poem long suspected as being quite late. And the only thing truly barring accepting this being different Gods being named as Frea's and Ing's fathers