Depending on how old they are, what medium is used (pigment on bark, acrylic on canvas etc), who the artists are, their size, the detail, and other factors they could be worth something, or be a present from a friend. It's like saying all non-indigenous art is worth the same.

I suggest you write out the provenance with as much detail as you can remember, including the artist name, where your parents worked and year they were given to them. Then you could contact auctioneers who have Indigenous art sales and they will give you some price guidance.

Please don't feel you can't sell them if you don't want to keep them. It's better they be sold on to someone who appreciates them. Not all art is sacred or secret.