Who is included on the Weasley's clock?

Question

The Weasleys have a magical clock in their home, The Burrow. It doesn't tell the time, but rather tells where and how the Weasley family members are.

Mrs Weasley glanced at the grandfather clock in the corner. Harry liked this clock. It was completely useless if you wanted to know the time, but otherwise very informative. It had nine golden hands, and each of them was engraved with one of the Weasley family's names. There were no numerals around the face, but descriptions of where each family member might be. 'Home', 'school' and 'work' were there, but there was also 'lost', 'hospital', 'prison' and, in the position where the number twelve would be on a normal clock, 'mortal peril'.

— Harry Potter and the Goblet of Fire, Chapter 10: "Mayhem at the Ministry", by J.K. Rowling

Are spouses represented on the clock as well? In the main 7 books, we see the marriage of Fleur Delacour to Bill Weasley and are informed of the marriages of Hermione Granger to Ron Weasley and of Harry Potter to Ginny Weasley.

Not only that, but Molly and Arthur have grandchildren as well. Victoire, Dominique, and Louis through Bill and Fleur, Molly and Lucy through Percy and Audrey, Fred and Roxanne through George and Angelina, Rose and Hugo through Ron and Hermione, and James, Albus, and Lily through Ginny and Harry. Are they all represented on the clock as well?

It seems that family members' hands aren't removed from the clock after they move out, since Bill and Charley were still represented even though they no longer lived at The Burrow.

So what are the criteria for inclusion on the clock?

Answer 1

It is never specified

The last time we see the clock is in HBP and it has 9 hands.

‘Then you just buck up your ideas, young man, before I decide you’re too immature to come with us!’ said Mrs Weasley angrily, snatching up her clock, all nine hands of which were still pointing at mortal peril, and balancing it on top of a pile of just-laundered towels. ‘And that goes for returning to Hogwarts, as well!’

Ron turned to stare incredulously at Harry as his mother hoisted the laundry basket and the teetering clock into her arms and stormed out of the room.
_{Half-Blood Prince - Chapter 6: Draco's Detour}

These nine people are obviously Mr and Mrs Weasley, and their 7 children: Charlie, Bill, Percy, George, Fred, Ron, and Ginny.

As vague as it is, the best we can say is that the criteria for inclusion on the clock is importance to Mrs Weasley (as it is her clock, see quote below) and being a member of the family (see quote above).

‘That will be a job for Fawkes when he has finished keeping a lookout for anybody approaching,’ said Dumbledore. ‘But she may already know … that excellent clock of hers …’

Harry knew Dumbledore was referring to the clock that told, not the time, but the whereabouts and conditions of the various Weasley family members, and with a pang he thought that Mr Weasley’s hand must, even now, be pointing at mortal peril.
_{Order of the Phoenix - Chapter 22: St Mungo’s Hospital for Magical Maladies and Injuries}

^{(all emphasis mine)}

What we know is that:

• Even after a child moves out, their hand is still on the clock, so it's not simply living at the Weasley's.
• Harry is never added to the clock (in the books at least) despite Mrs Weasley treating him like a son.
• We never see the clock again, we don't know if Fleur gets added after she marries Bill, or if Fred gets removed when he dies.

As far as I have been able to research, JKR has never added to the canon of the clock outside of the books. So as of right now, there is no way to know if anyone got added to the clock. Mrs Weasley cares a lot about her family, but it's unlikely she would care as much (defined as wanting to track their every move) for her children-in-law or grandchildren.