Would it be possible to be a love child of these two?
Could she have hidden the Dragonborn because she feared for her life?
I am excited by this possibility for a character. Would make killing Mercer cool.
Would I be a dunmer or imperial?
Mother and son, avenging the father.
A bit Sons of Anarchy. Lol

You'd need to be a dunmer as kids take after their mother.

And that sounds like a cool RP but..how old was Gallus?

If Karliah was pregnant when Gallus was killed it would make the DB 25. Presuming Dunmer had a 9 month pregnancy.
And the possible great grandchild of Tiber Septim

I think that's a great idea for an RP!

Name: Drayven
Race: Dunmer
Born:177
Ancestry:
Father- Gallus
Mother- Karliah Gm- drazli, GF- Tiber Septim, GGM- queen baranziah, GGF- Drayven Indoril (original nightingale).

In 176, after being framed for the murder of her lover, Gallus, Karliah fled in the black of night back to Morrowind and the city of Mournhold.
There, she left Drayven with the Indoril family, who raised him in secret.
In 198, word got to Morrowind of an increase in conflict between th Imperials and the Stormcloaks. Wary of Thalmor involvement, Drayven's uncle, told him his family story and the two of them took to the forests to live off the land. Drayven insisted they headed north to Skyrim.
Sometime in 201, they crossed the border near Shor's Watchtower pursuing a Cave bear.
One of their arrows narrowly missed an Imperial. The Imperial was part of General Tallus' patrol. They had just ambushed Ulfric Stormcloak. Drayven's uncle took responsibility for the stray arrow and they beheaded him on the spot. They beat Drayven, then threw him in the back of a cart that was headed for Helgen.

Super excited to get back from holidays to start my new character!
Would love any suggestions to do with lore and his background (as I know nothing from Morrowind except what I just researched). His family tree is very cool and it makes sense that he would be chosen as DB. I feel like I have unlocked a code! Lol

I agree with Aurora Winter: this is a cool idea. I may even steal this concept for one of my own games. Thank you for this inspiration!

Ok, so queen barenziah had affairs with both Tiber Septim and Drayven Indoril (nightingale), so Karliah could be the granddaughter of either.

Mercer is actually a Breton. Why not make a Dunmer character but with a more Breton appearance. That way you can combine the two. Elf ears obviously, dark eyes but maybe a more lighter human like skin.

I know right? its like how could I not have thought of this before?

That...would be stretching it, since every Septim had been dead for a long time.

Plus you'd have to go WAAAY further than just "great granchild" to be directly related to Tiber.