Almost incestuous premise....
Think about it. I know that the world over, distant cousins marrying might be kosher, but here in the states, it's like "Eeeeeeewww".
Miles' mom Sable and Jeff's mom Frankie are both first cousins of Caress and Alexis (Fallon's mom). Fallon married and slept with both Miles and Jeff.
And yes, I know that the west coast Colbys had NOTHING to do socially with the Denver Carringtons for almost 20 years, but when Fallon turned up in Los Angeles, as a new bride for Miles, I mean, SURELY any of the Colby women would have recognized her from newspapers, society magazines, or the like.
Of course, our soaps are high camp and escapism, but a few doses of reality could have made them a tad more believeable .