Perhaps a bloodline for the following:
having more than 20 children
having sex with more than 30 people
having multiple bastards
killing people in battlefield duels
hunting the white animal
winning a great holy war as a pagan
defeating a crusade as a muslim
forming prydain as a celt (king arthur bloodline)
lunatic bloodline sounds like fun

What about a Cthulhu bloodline? It definitely seems fitting to get SOME kind of recognition, after the fact you just beat FREAKING CTHULHU as a lunatic nonetheless. Maybe have something of a Cthulhu herald bloodline in which after doing a few minor quests or a full on story quest, you eventually summon Cthulhu and get a sick combat bloodline.

A custom kingdom-creator bloodline that gives buffs to vassals and culture would be nice

Originally posted by The Cure for Happiness:

A custom kingdom-creator bloodline that gives buffs to vassals and culture would be nice

This would be too easy for a bloodline. I might consider it for custom empire but even then it would probably too easy

Forming a Kingdom that never existed in the game's timeframe like say Ireland, Wales as a welshman.
a bloodline for winning what should be an impossible battle/war.

Some ideas (quality may vary)
* Bloodline for repelling the Aztec invasion (Stalwart blood of _)
Seems fairly self explanitory

* Bloodline for having way too many friends, plus maybe no negative opinion vassals and no revolt risk in any province? Maybe also no rivals? (Beloved blood of _). Possibly this should only be on the forge bloodline decision though. The main idea with this one is "beloved by all", so friends, vassals and peasants sort of thing.

* Special religious reformer bloodline if you have divine blood + fylkir + dogmatic (Divine blood)
Your character has set themselves up as a god. The should probably have a special bloodline (should replace the normal reformer one though)

* Jarls of India (taking a pagan religion with prepared invasion - Norse or Reformed Pagan with Daring - to India, except Bon or Zunist).

* Finding the Holy Grail / Holy Chalice (non-supernatural version)?

Originally posted by MuffinMann42:

Forming a Kingdom that never existed in the game's timeframe like say Ireland, Wales as a welshman.
a bloodline for winning what should be an impossible battle/war.

Although impactful storywise first suggestion is a really easy to achieve for a bloodline and it is hard to check if a title never existed in game. I am planning to add a bloodline for winning agaisnt a relatively really strong nation though.

Originally posted by Broken Sky:

Some ideas (quality may vary)
* Bloodline for repelling the Aztec invasion (Stalwart blood of _)
Seems fairly self explanitory

* Bloodline for having way too many friends, plus maybe no negative opinion vassals and no revolt risk in any province? Maybe also no rivals? (Beloved blood of _). Possibly this should only be on the forge bloodline decision though. The main idea with this one is "beloved by all", so friends, vassals and peasants sort of thing.

* Special religious reformer bloodline if you have divine blood + fylkir + dogmatic (Divine blood)
Your character has set themselves up as a god. The should probably have a special bloodline (should replace the normal reformer one though)

* Jarls of India (taking a pagan religion with prepared invasion - Norse or Reformed Pagan with Daring - to India, except Bon or Zunist).

* Finding the Holy Grail / Holy Chalice (non-supernatural version)?

Great ideas. Expect to see some of them added in the future

more ideas
Killing ghengis khan or anyone else with the title.
Defeating charlamagne as saxony, pehaps forming the germanic empire.
forming bosnia.
blood of hannibal barca for conquering rome as a pagan berber
playing as a norse pagan and holding the entire territory of germany, france, iberia and england as an empire.
immortal bloodline for completing the quest with the ability to share blood at will once every 30 years.
assyrian bloodline for ruling the lands of iraq, mosul, syria and jerusalem with the title "restorer of assyria" perhaps as a option in the intrigue menu.
blood of vercingetorix: as a breton rule the entire lands of france, brittony and occitan with no latins ruling it.
uniter of africa: as an african leader rule all of mali, kanem-bornu, maghreb, egypt, nubia and ethiopia. must do so as an african pagan. perhaps reformed.

immortal might be overpowered so maybe once every hundred years but your choice.

bloodline for the return of the Ephthalite empire?

Burn Irminsul: "The Fire of Christendom"

Building off of the africa idea. uniter of the steppes for ruling all of turan,tartarian and the pontic steppes.
uniter of europe: rule iberia, germany, france etc etc.

Originally posted by Elidurden123:

more ideas
Killing ghengis khan or anyone else with the title.
Defeating charlamagne as saxony, pehaps forming the germanic empire.
forming bosnia.
blood of hannibal barca for conquering rome as a pagan berber
playing as a norse pagan and holding the entire territory of germany, france, iberia and england as an empire.
immortal bloodline for completing the quest with the ability to share blood at will once every 30 years.
assyrian bloodline for ruling the lands of iraq, mosul, syria and jerusalem with the title "restorer of assyria" perhaps as a option in the intrigue menu.
blood of vercingetorix: as a breton rule the entire lands of france, brittony and occitan with no latins ruling it.
uniter of africa: as an african leader rule all of mali, kanem-bornu, maghreb, egypt, nubia and ethiopia. must do so as an african pagan. perhaps reformed.

Thanks for the ideas. I have taken note of them. Will add some of them with a few changes

Originally posted by Elidurden123:

immortal might be overpowered so maybe once every hundred years but your choice.

Immortal quest already has its own bloodline and there are other mods that deal with sharing immortality, healing etc. I don't think I will add any bloodline for immortality

Originally posted by Bogusik:

bloodline for the return of the Ephthalite empire?

Thanks for the idea. I added it to my list for planned bloodlines

Originally posted by Zachtan1234:

Burn Irminsul: "The Fire of Christendom"

Thanks for the idea. I am kinda conflicted on whether to add this one, I will consider it.

Maybe a shieldmaiden's bloodine for a shieldmaiden's who have won 10-25 duels, or take part of legendary gatherings that could only pass matrilinially like the blood of matilda or only get passed on to daughters. Other than generic modifiers like opinion or plus experience, it can also have a health bonus due to shieldmaiden's having one of the most bs events.

Looters bloodline for those who successfully aquire 3-5 artifacts via raiding.

Adveturer/explorer/traveler/wonderer bloodline for commanders or even courtiers who set foot on lands, get imprisoned, sent, or banished outside their original country's Diplomatic range. Or those who have been to 10 different courts.

Matriarchal bloodline for women who receive the "heavenly" event that gives them the attractive genetic trait or have both the genius and attractive trait and become ruler of their own country for 10 years. Only pass to daughters or matrilineal marriage.

Grand magus bloodline for those who hold the highest rank in the hermetic society for 20 years with learning above 40.

Judicator bloodline for passing 3 realm laws without fail during his/her lifetime.

First ruler bloodline for those who created their own country that doesnt have any previous historical rulers.

prester john bloodline for miaphysite christian who creates the empire of abbysinia.

And lastly saint thomas bloodline for creating a nestorian indian kingdom.

Originally posted by Elements08:

Maybe a shieldmaiden's bloodine for a shieldmaiden's who have won 10-25 duels, or take part of legendary gatherings that could only pass matrilinially like the blood of matilda or only get passed on to daughters. Other than generic modifiers like opinion or plus experience, it can also have a health bonus due to shieldmaiden's having one of the most bs events.

Looters bloodline for those who successfully aquire 3-5 artifacts via raiding.

Adveturer/explorer/traveler/wonderer bloodline for commanders or even courtiers who set foot on lands, get imprisoned, sent, or banished outside their original country's Diplomatic range. Or those who have been to 10 different courts.

Matriarchal bloodline for women who receive the "heavenly" event that gives them the attractive genetic trait or have both the genius and attractive trait and become ruler of their own country for 10 years. Only pass to daughters or matrilineal marriage.

Grand magus bloodline for those who hold the highest rank in the hermetic society for 20 years with learning above 40.

Judicator bloodline for passing 3 realm laws without fail during his/her lifetime.

First ruler bloodline for those who created their own country that doesnt have any previous historical rulers.

prester john bloodline for miaphysite christian who creates the empire of abbysinia.

And lastly saint thomas bloodline for creating a nestorian indian kingdom.

Thanks for great ideas