*Mentions of minor DH spoilers*
About Charlus and Dorea Potter and James's Parents:
On the Black Family Tree, the names Charlus Potter and Dorea Black are shown to be married. It also mentions that they have one son. Dorea was said to be born in 1920 and if James was born in 1960, then she would have been forty when her son was born. It goes along with the idea that James was born to his parents late in life, and his mother was a Black, so it supports the fact that Mr. and Mrs. Potter were fairly wealthy. It gives 1977 as Dorea's date of death, which makes her 57 when she died. That's rather young for someone to die of old age. But still, it would give something to prompt the maturing that James went through in his seventh year. And the Black seem to have very short life spans.
This also gives merit to the fact that James and Sirius already seemed to know each other on the Hogwarts Express. There is five years age difference between Dorea and Wallburga, nine between her and Orion. They had children around the same age, so it makes sense that they would be somewhat close, at least seeing each other at family events.
The con is that they are shown on the Black family tree. Knowing dear old Mrs. Black, she would have blasted off the people that took in Sirius in an instant. She did blast off Alphard just because he left Sirius some money when he died. Also, why didn't Sirius mention Dorea and Charlus when he and Harry were looking at the Tree in OotP? You think that he want to show Harry who his grandparents were. Also, he would have been proud to have the Potters' as his family. He took pride in having Andromeda as his cousin.
Basically, you could easily have Charlus and Dorea as James's parents, or could just make up a couple of OCs. At the least, Charlus was Mr. Potter's brother, making him James's uncle. I don't think that it's a coindence that they are on there.
~ Teresa
Link to the HP-Lexicon's Black Family Tree:
http://hp-lexicon.org/wizards/blackfamilytree.html