Does this mean an unpowered usb hub and a (for ex.) 4 in 1 usb Y cable would be the same?
No. A Hub has logic. Kind of like a Switch vs a Hub in Network terms if you are familiar.
I have yet to see a 4-1 Y cable for USB, and even if it exists, I can forsee horrible things like packet colission happening.
Just get a small hub and use the guts. use the single host cable from the pc, and plug the KB's cable into the hub.
I used a 2x2 hub (2 ports either side), and used the other port that is inaccessible from the outside for a stripped down 16GB pendrive. Instant storage. Admittedly though, it was on a M$ Rubberdome, and mainly to prove a point (I later sold it to the person who said it couldn't be done).