Good day,
yes, but that is, as far as I can tell, currently only possible when using an Type-I-Hypervisor like Xen or KVM for the “host machine”, but not with VirtualBox, which is what the original poster seems to aim for, if the sentence “guest system in VB running VPN” is anything to go by. Using Qubes would pretty definitely be able to pull something of, however, I’m rather unsure, whether this would bring a security advantage, or rather actually be worse then running Whonix “normally” inside a Qubes VM, since no other host system is as good as Qubes when it comes to providing security through separation. So installing for example plain Debian or Fedora on to of Qubes, to then install a virtual machine in there, on which you run Whonix, might actually be less smart then simply installing Whonix the “classical” way on an AppVM in Qubes. For more information on how to install Whonix inside a Qubes AppVM, please read: https://www.whonix.org/wiki/Qubes
Have a nice day,
Ego