Did Molly Weasley know Harry's parents?
No, Molly and Arthur Weasley
would not have heard or met Lily and James Potter during their (Molly and Arthur's) time at Hogwarts and you don't need to look at Pottermore or any secondary source to find this out.
Is Molly Weasley related to Sirius Black?
On the subject of Molly, it is interesting to note that she is
Sirius's cousin by marriage by virtue of her marriage to Arthur. However, the way Sirius mentions their relationship, it sounds as though she is related to him by marriage through some other relative as well.
What does Molly Weasley do for a living?
During the second rise of Voldemort, Molly joined the Order of the Phoenix. She took on the responsibility of making
12 Grimmauld Place into a place fit for human habitation. Molly does often do the cooking, but she makes everyone chip in and help.
How old was Molly Weasley when she died?
But it sail Molly Weasley lived to the age of
100. It said she lived alone, so I'm assuming Arthur died before the age of 100. It also said she was having problems remembering things, so her mental state wasn't so great.
How much older are the twins than Ginny?
Fred and George Weasley are the twin older brothers of Ron Weasley and Ginny Weasley. They are
around two years older than Ron and Harry, and were in Gryffindor, following in the footsteps of their family. They are tricksters, always inventing new tricks and playing practical jokes on their schoolmates and teachers.