I Had An Idea For A Plot Twist...
It was back when "90210" was still on. We never got to see Adrianna's dad throughout the whole series.
Here's the plot twist I had in mind:
In the original 90210 back in the 90's, it's revealed that Mel Silver, David's father, cheated on Kelly's mom Jackie (who did appear on the show and died of cancer in the 2nd season). It turned out he was seeing a bunch of women behind her back, so she divorced him. Well, what if one of those women happened to be Adrianna's mom? Mel dated her and even slept with her and Adrianna was born as a result?
That would make Mel Ade's dad and her and Silver sisters!