Beorn....

[Legolas]

I have heard that he is some sort of half-man, half-maia breed with the ability to shapechange but thats only what I have heard and by no means do I believe it true. If anyone does know more about and/or what books might talk about his origin and ancestry that would be great, thanks.

This is a false claim. He can shift shape, but he's not half-Maia. Keeper of Dol Goldur, a member of this forum, made a thread outlining a theory that Beorn was related to Radagast, but it isn't supported anywhere by Tolkien - Beorn was a man.

One should look no further than Tolkien himself when looking for an explanation of such matters.

Beorn was a man.

Tolkien, in Letter No. 144:

Beorn is dead; see vol. I p. 241. He appeared in The Hobbit. It was then the year Third Age 2940 (Shire-reckoning 1340). We are now in the years 3018-19 (1418-19). Though a skin-changer and no doubt a bit of a magician, Beorn was a Man.

Gandalf says...

'A man; no doubt a bit of a sorceror, but a man.'

Aragorn, speaking to Legolas and Gimli about the Rohirrim, gives information on Beorn's ancestry.

It was in forgotten years long ago that Eorl the Young brought them out of the North, and their kinship is rather with the Bardings of Dale, and with Beornings of the Wood, among whom may still be seen many men tall and fair, as are the Riders of Rohan.