AMC: Adam and Erica Kendall and JAR

When in the series of events was Erica's second marriage to Adam? (Actually
still her first one as they weren't legally divorced?)

I know it was after Bianca's birth as her legitimacy was an issue. And I
know it didn't last long. Was it before or after Adam's marriage to Brooke?
Before or after Dixie and JAR? Before or after Kendall was revealed?

What I'm getting at is Kendall and JAR are/were stepbrother and stepsister.
But was there ever a time they considered themselves to be so?

Jo