We don't know anything about these two characters in the series. However, we know that they took care of Sirius Black when he ran away from his home. They took him as a second son. It seems that they are dead. Mr. Potter was presumably the "grandfather with knobbly knees" that Harry saw in the Mirror of Erised.
James Potter is a fictional character in the Harry Potter books. He was born c. 1960 in England. He attended Hogwarts School of Witchcraft and Wizardry c. 1970 to c. 1978. It was in Hogwarts where he met his future wife Lily Evans. After finishing Hogwarts, James and Lily married and had a son, whom they named Harry. James and Lily belonged to an organization called the Order of the Phoenix, which was created for wizards who wanted to battle Lord Voldemort. On October 31, 1981, James and Lily were murdered by Lord Voldemort himself.
Lily entered Hogwarts School of Witchcraft and Wizardry in 1971 as a member of the Gryffindor House. Lily met her husband, James Potter, at Hogwarts, but for most of the time they were there, she regarded him as an arrogant fool. They only had one child, who grew to be a year old before they were both murdered by Voldemort. She was considered a talented student and was named Head Girl during the last year of her studies. She graduated in 1978. Soon after her graduation she married her old friend James Potter. On July 31, 1980 they had a son named Harry James Potter. At the time Lily and her husband were members of the Order of the Phoenix, an organization of sorcerers opposing the ambitious Lord Voldemort and his Death Eaters. On October 31, 1981 Lily and her family faced an attack by Lord Voldemort himself. Their confrontation ended with first James and then Lily dead and Voldemort himself barely alive. After their deaths, their son was taken in by his closest living relative who happened to be her sister Petunia, married to Vernon Dursley.
Since Lily sacrificed herself to save Harry from Lord Voldemort she gave Harry a defence that Voldemort has always hated and to his cost, underestimated. Later in Harry Potter and the Philosopher's Stone, Professor Quirrell, acting as host to Voldemort, attempts to attack Harry to gain the philosopher's stone, but is destroyed by the attempt, and Voldemort returned to his prior non-corporeal state. Harry is safe with her sister, Petunia, because Lily's blood runs in her veins, as well as Harry's.
Though Harry bears a great resemblance to his father, it is often noted that he has his Lily's green eyes; several rumours regarding the forthcoming events of the sixth and seventh Harry Potter books regard this detail as significant.
Vernon Dursley is a fictional character from the Harry Potter series of novels, by J. K. Rowling. He is married to Petunia and they have a son named Dudley. Through his wife's sister Lily, he is the uncle of her son Harry Potter. Vernon is described as a big, beefy man, with hardly any neck, and a large mustache. He is the director of a drill-making company called "Grunnings". He is a muggle, and detests all magical things, especially his nephew Harry. He and his wife, Petunia, have grudgingly raised Harry from an early age, denying him any information about the magical world, including his parents.
Petunia Evans Dursley is a fictional character from the Harry Potter series by J. K. Rowling. She was born Petunia Evans and her whole family was made up of muggles, except for her younger sister Lily who was a Muggle-born witch. Their parents were proud of having a witch in the family. However, Petunia saw her as a freak.
At some point she met Vernon Dursley and married him. On June 22, 1980 they had a son named Dudley. Petunia Dursley hadn't seen her sister for years and usually pretended she didn't have a sister. However one day she discovered her nephew; Harry on her doorstop.
Warning: Spoilers follow
There was a note left with baby Harry, which explained that his parents Lily and James had been killed by Lord Voldemort, how Lily Potter had sacrificed her self to save her son's life and how if he lived with his mother's relatives he would be protected from Lord Voldemort.
Petunia and Vernon agreed to raise Harry, but decided they would keep him as downtrodden as possible in order to squash the magic out of him; they never told him how his parents died, and said they died in a car crash.
When Harry started getting letters asking him to come to Hogwarts, Vernon and Petunia tried to run but Hagrid caught up with them at the hut-on-the-rock. He told Harry the true story of how his parents died and took him to Hogwarts. The Dursleys have since taken to ignoring Harry.
Dudley was born on June 22, 1980. He is the first and only son of Vernon and Petunia Dursley, a nephew to Marjorie Dursley and Lily Evans (respectively his father's and mother's sisters), nephew by marriage to James Potter, and first cousin to Harry James Potter. Through his relatives Dudley seems to be relatively well-connected in both the Muggle and the wizarding world. He has loving parents who seem to have spoiled him since birth. Dudley is somewhat egotistic. While growing up he revealed a cruel side of his personality in his relationship with his cousin Harry. He seems to have enjoyed any opportunity to torment and humiliate him. In 1991 Harry first discovered his magical powers, while Dudley seems to be a common Muggle. In addition to lacking in magical potential, Dudley also seems to be lacking in intelligence and social skills. On the other hand, Dudley is strong and athletic. He has taken an interest in boxing and seems skilled in it. Losing his cousin and favourite victim to Hogwarts seems to have turned his attention to other targets. By the time of Harry Potter and the Order of the Phoenix he had joined a gang of similarly minded teenagers. They enjoy intimidating those younger and/or weaker than them and have been involved in several acts of vandalism. His parents seem to be unaware of it. His cousin on the other hand is both aware and disapproving of Dudley's recent activities.
Majorie "Marge" Dursley is Vernon Dursley's sister. Though she isn't a blood relative of Harry, he has been forced to call her "Aunt Marge." Aunt Marge lives out in the county, where she breeds bulldogs. Due to this, she hardly ever visits Privet Drive, to Harry's great delight. However, each of her visits stands out in Harry's mind. For example, when Harry was nine, Ripper, Aunt Marge's favorite dog, chased him up a tree. Aunt Marge didn't call the dog down until after midnight.
Her most recent visit was in Harry Potter and the Prisoner of Azkaban, when Harry quite literally blew her up. Under normal circumstances he might have been expelled, but with Sirius Black on the loose he was allowed to remain at school (although he wasn't told this immediately).
Warning: Spoilers follow
Mr. and Mrs. Evans have never shown up, only been referred to, but there was a boy named Mark Evans mentioned in the first chapter of Harry Potter and the Order of the Phoenix. On page 13 (American) the book says:
"So who've you been beating up tonight?" Harry asked, his grin fading. "Another ten-year old? I know you did Mark Evans two nights ago."
General speculation in the internet realm of Harry Potter is that Mark is a relative of Lily Evans in some way, and, as he is ten, he will be entering Hogwarts next year. This short passage is another demonstration of the genius J.K. Rowling has with plot devices and foreshadowing.Family tree of Harry Potter
Mr. Dursley--+--Mrs. Dursley Mr. Evans--+--Mrs. Evans Mr. Potter
| | +
+----+----+ +----+----+ Mrs. Potter
| | | | |
Marjorie Dursley Vernon Dursley--+--Petunia Evans Lily Evans--+--James Potter
| |
Dudley Dursley Harry Potter
Mr. and Mrs. Potter
James Potter
Lily Evans Potter
Vernon Dursley
Petunia Evans Dursley
Dudley Dursley
Marjorie Dursley
Mr. and Mrs. Evans
The mother and father of Lily and Petunia Evans. They were both muggles as was their daughter Petunia; Lily turned out to be a witch. They were said to be "proud to have a witch in the family"; however, Petunia thought Lily was a "freak". Petunia is grown and married (to Vernon Dursley), and Lily died October 31st, 1981.