I think it'd be worth to put this information here, because it is quite a common problem. To increase the buffer of your keyboard (to allow you to press more keys at once), do the following:

Press the Windows logo key and R at the same time.

Type
regedit.

Go HKEY_LOCAL_MACHINE >> SYSTEM >> CurrentControlSet >> Services >> Kbdclass >> Parameters

Find
KeyboardDataQueueSize.

There, increase the value to an hexadecimal value of your liking. The default is 100 (64 in hexa).
There, now you can play with a friend in the same keyboard.
