I currently have four characters out on kidnap missions and they have not returned its been 45+ days now. 

I can't call them back and I can't sell them ? 

So how do I fix this ? if I can. 

oh no, a return of the event queue bug.

as near as i can tell, in this situation the "return from mission" events are getting blocked from firing off their dialog windows, preventing them from being processed and cleared out.  two or three patches ago this hit the same area you're experiencing, and also pregnancies.

it was generally triggered by having a "return form expedition" or "birth" event happen the same day that an invasion happens.

this could be fixed by changing the "fire event" check from "days remaining till event = 0" to "days remaining till event <=0"

or actually fixing the event queue such that it does not skip events at all anymore.

i cannot explain why keepherdev has not done the simple fix of changing that "=" to a "<=" though.  it's such a simple fix.