This takes place after the latest Flash finale so I read at your own risk of your not caught up. Disclaimer: I don't own Supergirl or the Flash.
Kara
As we reached the loft, I could tell Mara was extremely uncomfortable with Mon-El's question. Before she could answer, suddenly a portal opened and Barry came out.
"Mara! "We found you!" A girl exclaimed next to Barry.
"Nora! You found your dad!"
"Yes! It's the least I could do since, well, you know..."
"Yeah, which I am still extremely mad at you about."
Nora just laughed sheepishly.
"What is going on here?" I finally ask looking over at an equally confused Mon-El.
"Apparently this is my daughter Nora, from the future." Barry said.
"Who is she?" He asked.
"Mara is our future daughter." Mon-El said with both pride and confusion as to what's going on.
Suddenly another portal opens up.
"Oh you have got to be kidding me!" Nora cries.
"Everyone get ready!" I yell.
Suddenly a young boy comes through the portal.
"Cometgirl!" He yells.
"Cometgirl?" Mon-El asks knowingly. Whenever he looks into my eyes he always says they are his comets. It's fitting our daughter is named Cometgirl.
"Jack!" Mara yells as she runs into his arms and kisses him.
"What is going on here!" Mon-El yells, not liking the sight of his future daughter in the arms of an unknown teen.
"Who are you!" He yells again.
"Mon-El, calm down."
"Kara! He just kissed our daughter! How do you expect me to be calm?"
I say nothing in return and stroke his hand softly and lovingly.
"I am Jack, Oliver and Felicity's future son. And Mara's boyfriend sir."