"...both are united through Love."
Apparently, you are referring to "cause and effect being united" in any other regard than what is evidenced in most human behaviors. Few people are united through Love, unless their Love is for all of the same thing(s). Not everyone loves when they exert their own causes upon others in the worldly community.
However, in reference to a more Divine aspect of Will, it becomes interesting to contemplate "Will" (as only "desire" when not in an active state) in comparison to, and in relation with, the other two forces of the Divine Trinity - namely : Wisdom ("Love") & Activity ("animated motivation").
"Will", pure and simple, is just the "desire" to act upon some aspect of reality. Divine Thought wouldn't do this without sincere contemplation, nor would it occur with "reckless abandon" if it were a "Self-Loving" energy in the first place.
A non-self-loving energy would, by nature be a destructive force.
(think about it - "Will" in a pure and raw form : anything that Will acts upon doesn't likely improve that pre-existing "thing" - it destroys it, so as to replace "what once was" with a newly personalized [object of] Desire)
Alternatively, you might consider that Will either "replaces an older version" of something, or it changes an original "something" into a (so-called) "improved" version. But in either case - for better or for worse - that cannot occur without the "Activity of doing so" - in other words; "Will is not acting on its own."
So, to me, the "unity" is a prerequisite for not only "Will" alone (unto Itself) - but with the "Loving Direction" that "Will" chooses to go in.