How long has it been since you have seen each other?
To me, this sentence seems to be somewhat awkward and not grammatical.
In fact that sentence is OK. " is simpler, however, and does the same job.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
In fact that sentence is OK. "How long is it since you have seen each other?" is simpler, however, and does the same job.