The Mother Surprise
"Daria, now that you and Jane are adults, well eighteen anyway," Helen began nervously.
"Jane," Vincent said quickly as he headed for the door to Schloss Morgendorffer. "I'm not your father but I'll always be your dad. Gotta catch that plane."
"Wait, Dad," Jane said to his retreating back. "Wait. What? Isn't that a bluegrass song? What?"
"Daria," Jake began. "There's another reason we moved to Lawndale besides your mother landing a great job."
Daria and Jane instinctively felt something momentous coming on. So momentous that they held hands on the couch and did not mind when Quinn joined them.
The three teens looked at Helen, Jake and Jane's mother, Amanda who were all nervously hemming and hawing.
"Jane," it was Amanda's turn now. "Before I had you, Vincent and I were going through a rough patch."
"Yeah," Jake chimed in. "And I wasn't sure about marrying your mother yet either."
"I love you, Daria. You too, Jane." Helen added to the confusion.
"Amanda and I and well, everyone, knew each other in college. We kept in touch." Jake attempted again. "So one night about nineteen years ago. Amanda and I got together and had a bit of, uhm, something and well…"
"You and Jane are fraternal twins." Amanda could not keep it in any longer.
Daria was the first to break the shocked silence. She stood up and turned to Jane.
"Well, I guess that means the wedding's off and I need to return this." She slipped her engagement ring off her finger and handed it to Jane.
Alternate ending:
Daria was the first to break the shocked silence. She turned to Jane on the couch.
"So, you mean what we did last night was…"
"Ewww," Quinn cut her off.
Alternate alternate ending:
Daria was the first to break the shocked silence. She turned to Jane on the couch.
"So, you mean what we did in my room last night was i…"
"Ewww," Quinn cut her off.
"Illegal in the state of Maryland," Jane finished for Daria. She stood up and extended her hand to Daria. "Wanna do it again, sis?"
"Ewww," said Jake, Helen, Amanda and Quinn.
"Oh, Daddy, can I borrow the car later?" Jane asked Jake.
A numbed Jake could only hold out the keys as Jane led Daria up the stairs.
I have an alternate alternate alternate ending in mind involving Daria breaking off her engagement with Jane. She then would turn to lawyer-mom Helen and inquire about the legality of marrying her half-brother Trent. But I couldn't quite make the dialogue work so I will leave that to your imagination.