How to distribute my broadband bandwidth between 4 PCs?

[Fuzz]

OK people I need some help here!

My cousin and his 2 brothers what to get broadband and share it between their 3 PCs. I recomended going wireless as the PCs are split over 3 floors.
That was the easy bit the problem is this.

Their dad since discovering the internet has become a download junkie (when I mean download junkie, I mean BIG TIME!).
I few months ago when he had a free broadband trial he totaly abused that connection, his PC was never off!

Now that his 3 sons want to get broadband he wants to get it as well so that all 4 PCs use the same connection.
No problem I hear you say, but the guys don't want him to abuse the connection to the extent where their connection seems slow as he is downloading all the time or for him to hit the cap limit in 2 hours.

The only solution I can think of (apart from them moving out or having a seperate connection) is:

a) A hardware / software solution what will dynamically split the broadband bandwidth acording to how many PCs are currently connected.
E.G. 4Mb connection with 2 PCs on = 2Mb each, 4Mb connection with 4 PCs on = 1Mb each.

b) A hardware / software solution what will let you pre assign how much of the broadband bandwidth each PC can use.
E.G. 4Mb connection = 1Mb to each of the PCs whether they are switched on or not.
or 4Mb connection = 1.5Mb to 2 PCs (each) and 512Kb to 2 PCs (each), Totaling 4Mb.

Solution 'A' is the prefered option but if you have any other ideas then please post.

As much help or (pointers) would be greatly apreciated everybody!

Many Thanks In Advance

[directhex]

you can do traffic shaping with any unix-style os. BSD tends to do much better at it than Linux. When I was at uni, we had a 2mbit line between 6 people. The traffic was shaped such that all packets of a certain type (games) had no restrictions & were automatically sent before anything else, then HTTP traffic, then upload, with a 64k upload cap per machine, and downloads uncapped, but fairly shared between all people downloading at once (i.e. 4 downloaders, equal share 512k each)

[Fuzz]

If posible I need a windows solution if it's gonna be software based (sorry for not stating that earlier on).

[aidanjt]

undoable with windows im afraid, i've even looked at commercial windows routing software and it still doesn't come close to cutting the mustard compaired to *NIX in terms of network load ballancing and routing performance.

[ajbrun]

I have no knowledge of these things, but:

Says server, but might work
It says bandwidth restrictions

Those are the ones I've seen on the 1st page, but if you want more, go here. As I said, they may or may not work .