A few famous Indian dynasties that can become candidates for bloodline traits -
Maurya -
The grand imperial dynasty of course, created the most powerful empire of the Hellenistic era, kicked out the Greeks, unified India, created a stable and well organized government structure, began colonizing Southeast Asia and ushered in a golden age of civilization and imperial power that would not be matched until 500 years later.
After their empire ended, their descendents were still around until early medieval era.
Nanda -
Founders of the very first major empire in Indian history after taking over Magadh. They were about to have a massive war against Alexander with their huge army, but later got toppled by rebellion of Chandragupta Maurya like only 20 years before the game's start.
Their descendents still exist in Maurya lands.
Shunga -
The powerful, religious family of warrior priests that overthrew the Mauryan Empire in a coup, rebuilt the army and then went on to defeat Bactrian and Seleucid invasions. Split India into a north-south diarchy and only stuck around for a while, but still managed to restore stability and create a golden age.
They always start off as one of the noble families under Mauryan Empire, at least in my game.
Haryanka -
The very powerful militarist dynasty that ruled the old Magadh kingdom during Achaemenid era. Their relentless wars of conquest spanned entire northern India. They were the ones who brought Magadh from a small state into a large kingdom, hegemon of Aryavarta and paved way for Nanda and Maurya empires.
Also built the largest city in the world in their time - Pataliputra. And invented the concept of scythed chariots.
Both Buddha and Mahavira, founders of Buddhism and Jainism respectively, spent significant portion of their lives in Haryanka kingdom.
They were kinda like what Qin dynasty was to China, and they can still be found as characters/nobles in Mauryan Empire.
Brihadratha -
One of the oldest dynasties in India, and the very founders of kingdom of Magadh. They have been around since late bronze age, and many of their members have become legendary and mentioned in most Vedic literature and epics, with their own heroes and champions.
Can still be found as characters in Mauryan Empire.
Kuru - (or more correctly, Kaurava)
Another very famous old dynasty from the bronze age, they are legendary protagonists of major Indian epics like Mahabharat, and helped shaped the Vedic religion. They also found the kingdom of Kuru and its capital, the city of Hastinapur (later became the imperial city of Delhi by medieval era). They were masters of chariot warfare, and helped shape Vedic culture in the late bronze age/early iron age.
Their descendents still exist as characters in Mauryan Empire.
Pauravid - (or more correctly, Paurava)
The dynasty of King Puru (or Porus in Greek), the man who fought Alexander to a standstill on the Indus, and immediately earned his respect and became a vassal Satrap, before being assassinated by Diadochi general Eudemos. In the chaos that followed, the Paurava kingdom fell into civil wars and Greek invasions before being conquered by Mauryan Empire.
Paurava family still rules a small eastern remnant state under Mauryan control as vassals.
Haihaya -
A very prestigious dynasty that emerged from the earliest days of Indian civilization in middle and late bronze age. They went southwards and built a stable, powerful kingdom around Narmada river valley, and founded the large capital city of Mahishmati in late bronze/early iron age (that city became stuff of legends and stories in its own way). Some of their kings and princes also became legendary, participated in many celebrated major wars over the centuries.
A cadet house also founded the kingdom of Avanti, although they only ruled it for a short time before their own minister usurped the kingdom and drove them out.
They are still present, ruling their old kingdom (named Mahishmandal in game) in a diminished and weakened state as a vassal under Mauryan Empire. Dynasties of their descendents are present all around CK2/CK3.
Pradyota -
The royal dynasty of the Avanti kingdom, and the ones who brought it to the peak of power after launching a coup against Haihaya dynasty. Avanti became the second most powerful kingdom in India after Magadh. They ruled over a kingdom famous for learning and knowledge (their capital Ujjayini was like Athens of India in terms of learning and philosophy), as well as controlling major trade routes. The war between Avanti and Magadh was the final major war of the Vedic era/rise of Magadh.
Ironically, despite the power and stability of their kingdom, their dynasty was more famous for repeated internal treachery and intrigue.
Their family is still present in Mauryan Empire. In fact as Maurya you can assign them governorship of the kingdom they once ruled.
And then, in the south.
Pandya -
Very famous dynasty that essentially (for all practical purpose) founded the Tamil culture and the power base of southern Indian kingdoms. They became hegemon of southern India whenever northern powers weakened. They would go on create a powerful empire in the medieval era (both before and after Chola), and their final remnant is still present and playable in 1444 EU4 start date.
Chola -
Another famous southern Indian dynasty, who would serve as vassals of various empires before starting a cultural, architectural and religious revolution in the early medieval era.
They maintained the largest maritime empire in medieval Asia, conquered southeast Asia and all of southern India, built huge temples and cities that are still major urban centers, and created a golden age that rivaled that of contemporary Tang and Song dynasty China, and Vijayanagar empire would later restore in EU4 timeline.
Together, Chola and Pandya are counted one of the longest reigning dynasties in history, and you can see why.
Vijyaya - The founding dynasty of the kingdom of Anuradhapur in Lanka. They led a huge migration of people from northern India to colonize Lanka far in the south, which became the Sinhala people. Built their kingdom on stable irrigation and agriculture while surviving as vassals of various Indian empires as they came and went. The result was a system so stable and long lasting, they are even present in CK2/CK3 era 1300 years later.
And I've not even mentioned some of other ones. Some of them are notable dynasties I saw in earlier versions of Imperator, that are no longer present because their characters probably got deleted -
- Satvahan - the Mauryan imperial viceroys of the south, and the first to declare independence when Mauryan Empire collapsed. They formed their own powerful and prosperous empire that survived well into the antiquity. They form the southern part of that Shunga-Satvahan diarchy that split India.
- Shishunaga - the dynasty that ruled Magadh between Haryanka and Nanda, finished the conquest of Avanti, strengthened the roots of imperialism that followed later on, and became the first regal patrons of Buddhism.
- Kanva - successors to the Shunga (which had succeeded Maurya, remember), last major imperial dynasty to rule northern India until Kushan and Gupta Empire.
- Shakya - the famous dynasty of Buddha himself, and rulers of Kapilavastu. In earlier versions their family was visible (if I recall correctly), before being cut like the rest.
- Kirata - ruled a famous warlike jungle tribe during the bronze age, still rule a tribal kingdom (so called "Atavia") as vassal of Mauryan Empire.
- Vatsa - cadet branch of Kaurava/Kuru dynasty that ruled a powerful, heavily urbanized river kingdom. Characters of this family can still be randomly present in Mauryan Empire at start.
Now who among these should be given bloodlines is up to the devs.
But bloodlines in my opinion won't really work well until they restore the old family system. Minor characters can't do anything or have kids, simply because someone arbitrarily thought that was a really good idea.