Aberforth and Mundungus’s business dealings?

By: Gina

Aberforth is Dumbledore’s brother, who was once arrested for ‘practising inappropriate charms on a goat’.  Evidence has proved that the barman in the hogs head is in fact Aberforth himself. For instance, when Harry and co first go in there, Harry can smell goats, and the man is described as tall and thin and vaguely familiar to Harry.
Now, in the Half Blood Prince, I came across a clue that only now, even after countless times of reading, has jumped out at me:

Two men a little ahead of them, standing just outside the three broomsticks. One was very tall and thin; squinting through his rain washed glasses Harry recognised the man as the barman in the Hogs Head. As Harry, Ron and Hermione drew closer, the barman drew his cloak more tightly around his neck and walked away, leaving the shorter man to fumble with something in his arms. They were barely feet from him when Harry realised who the man was.
“Mundungus!”
The squat bandy-legged man with straggly ginger hair jumped and dropped an ancient suitcase, which burst open, releasing what looked like the entire contents of a junk shop window.

Mundungus, it turns out, has a hoard of silver from Sirius’s house. So what is Aberforth doing with Mundungus, is he possibly supplying him with Sirius’s valuable possessions from number 12 Grimmauld Place? Or was he merely trying to stop Mundungus from selling it? But, we also know that the Bar man, (alias Aberforth) banned Mundungus from the Hog’s Head 20 years ago, as it says in The Order Of The Phoenix. So what is he doing meeting with Mundungus if Aberforth banned him?

Later on, when Harry tells Dumbledore about Mundungus, Dumbledore already knows and tells him ‘ah yes, I am already aware that Mundungus has been treating your inheritance with light fingered contempt,’
‘I rather think he dreads facing me. However, rest assured that he will not be making away with any more of Sirius’s old possessions.’
So Dumbledore already knew, was that because Aberforth had told him, or Mundungus had? Having a brother working in a Pub next to your school is very handy when you want to know what’s going on. Aberforth has never seemed a very friendly type, but he was in the order last time Voldemort was in power, so does that mean he is in the order again now?
If so, surely he would stop Mundungus from stealing stuff from headquarters?

All very mysterious….