Muggles' Guide to Harry Potter/Characters/Jack Sloper

Overview
Jack Sloper is a Beater on the Gryffindor Quidditch team. Along with Andrew Kirke, he takes over for Fred and George Weasley after the latter are suspended from playing Quidditch.

Order of the Phoenix
In the last meeting of Dumbledore's Army before Christmas, Angelina Johnson tells Harry that they have finally managed to get replacement Beaters. Alicia Spinnet says the new beaters are Andrew Kirke and Jack Sloper, and that they are nowhere as good as Fred and George, but were the best of a very bad lot.

On February 14th, Ron says that he can't go to Hogsmeade, because Angelina wants a full day's practice. Ron is skeptical that it will help, because Sloper and Kirke are even worse than he is.

The following weekend, in the match against Ravenclaw, it is remarked that one of the low points of the game is Sloper swinging at a Bludger, missing, and hitting Angelina in the mouth with his bat.

Sloper is later mentioned at Easter Break. Ginny, meeting Harry in the library, tells him that Quidditch practice had ended early because Ron had had to take Sloper to the Hospital Wing. They are not sure what happened, but they think he knocked himself out with his own bat.

Half-Blood Prince
Jack carries a message from Albus Dumbledore to Harry, then asks Harry when try-outs are.

When try-outs happen two weeks later, Jack is passed over; the new Beaters are Jimmy Peakes and Ritchie Coote.

Strengths
Jack appears to have at least some knowledge of Quidditch; although he is comically shown to not be a particularly good Beater, he does successfully try out for the position (and, in fact, is part of a team that wins the Quidditch Cup). He is also keen to try out again in the following year.

Although he delivers a message to Harry at one point, this may just be coincidental. Anyone can deliver a message; Jack was just an available Gryffindor.

Weaknesses
Despite liking Quidditch, Jack is not very good at it. He does try out again for the position in Harry's sixth year, but is not successful.

Relationships with Other Characters
Jack is presumably on relatively good terms with Andrew Kirke, as they work together as Beaters on the Quidditch team. He also knows Harry by association, as he addresses him as "Harry" when delivering his message.

Questions

 * 1) Why is Jack on the Quidditch team when he lacks the necessary ability?
 * 2) How old do you think Jack might be? Why is this?