Pendrives are USB slave devices, USB slave devices can not communicate directly with USB slave devices. There have been a few standards that were toyed with such as USB on the go, which have failed due to no one adopting the standards, for general purpose USB slave devices, a third medium is absolutely required. This does not have to be a PC mind you! Something like the Viniculum chips support both usb slave and host support for HID and mass storage types devices which might allow what you want.