Expansion between two NAS drives

I own a My Book Live Duo with 2 x 3TB hard drives which I use as a single volume. I am now considering buying a WD My Cloud EX2 with 2 x 3TB hard drives.

Is it possible to join the My Book Live Duo and My Cloud EX2 via USB to form a 12 TB volume which can be configured into various RAID modes. I know I can add USB HDs to form expansion, but have not seen any info on whether this is pssible with another NAS device. 

I’m assuming that if I were able to join the two I might negate the cloud functions of the My Cloud, but someone probably knows more than me on this subject.

Thanks for any suggestions.

You’ve posted this into the wrong forum section - this one is for the MyCloud Mirror, which is an entirely different product from either of the two you mention (both of which have their own sections here).

But my expectation would be that your answer would be no, at least based on my experience of the MCM. There you can plug another drive or two into its USB ports, but they appear just as additional shares (as you already know from your comments) and cannot be used as part of the raid functionality as they are not directly under the control of the firmware of the main unit (the MCM or EX2).