Official time-line notes (excerpts):
12th-14th centuries: According to some dates given, Alucard was born in 1397 but this does not make any sense as I'll explain in a second.
15th century: Lisa, Dracula's second wife (presumably the reincarnation of his first, Elisabetha), was condemned to death by Inquisition and burned at the stake in front of her son, Alucard. Dracula's grief and hatred was profound. He blamed this on all of humanity, and hated humans.
In 1476, his war with the humans and the Belmonts began.
Here's where the dates get a bit weird. Konami places Lisa's death in 1470. However, SotN's manual places Alucard's birth around 1397. Assuming that Lisa would have been in teens when Alucard was born, placing her own birth round about 1380; since her natural life would probably end around 1450, it seems likely that her execution took place some time between 1400 and 1450. But it gets even weirder than that because Lisa looked young when she died- in her 30's, perhaps. AND Castlevania Judgment places her death at 1475, a year before Castlevania III, BUT Lyudmil comes to Alucard some time (perhaps years) after Lisa's death and says "I'll be 22 this year. I am merely a few years older than you." This would mean that Alucard is at most TWENTY when he fights his father.
SotN's manual also stated Dracula's age to be approximately 800, placing his birth around 997, while Mathias Cronqvist (being 32 in 1094) was born in 1062.
Assuming an error of at most 65 years either way in both cases, Alucard's birth could have taken place any time between 1332 and 1462; this is very interesting because the REAL Dracula, Vlad... his first son was born in 1462.
Considering that Alucard was old enough to remember his mother's last words, he would probably have been no younger than 5 at the time of Lisa's execution (although dhampirs may learn at an accelerated rate), placing Lisa's death any time between 1337 and 1467.
We can assume that all of the characters were born later than they were stated to be but that Lisa died before she was stated to in Judgment; this also makes sense if you know the irl history of Vlad.
Basically, if you're trying to set up a time-line, just pick what you want. I've written my own interpretation. >_>
1450: (non-canon) Sonia Belmont takes up the Vampire Killer whip and swears to avenge her grandfather after he is killed by Dracula's minions. (this makes no sense, as Dracula did not start killing the crap out of humans yet, not even in real life >_>) During her search, she meets and forms a strong bond with her enemy's son, Alucard. (Alucard was still with one or both of his parents at this time) After vanquishing the Count, Sonia vows that if Dracula returns after her lifetime, others will take her place and defeat him. (The game's creators intended Sonia to be the first Belmont to battle and defeat Dracula.) It's implied that she has Alucard's child (... this makes no sense at all... >_>)
About 1470-1471: Carmilla and other children of the night cause darkness in humans hearts to launch the great witch trials. Many of Sypha Belnades' fellow sisters are killed in the events. Later, Sypha Belnades becomes a hunter for the Church.
1476: (Castlevania III: Dracula's Curse) Dracula's war with humanity. The Belmont clan had been feared for their supernatural powers and exiled from Transylvania, but with the impending danger on his hometown of Wallachia, Trevor Belmont answers the call to duty. Picking up the Vampire Killer whip bestowed to him by the Poltergeist King (this may be Pumpkin... perhaps Leon had Pumpkin hold the Vampire Killer until Mathias was finally located? Hmm), Trevor goes to battle, meeting up with three companions along the way- Grant DaNasty, Sypha Belnades, and Alucard, the dhampir son of Dracula.
Grant's clan was wiped out, courtesy of Dracula (the 'Danesti' clan was a TRUE family in opposition to Dracula, and he hunted them as soon as he came to power) and he was turned into a monster. Sypha was ordered to attack Dracula, and when she tried she was turned into a statue but Trevor frees her; I can't decide whether or not he knew immediately that Sypha was female.
Because Trevor was the first person to ever destroy Dracula, the Belmonts were welcome again in Wallachia. Sypha and Trevor fall in love (to Grant's dismay) and have children. The magic power of the Belnades is inherited by future Belmonts (Juste Belmont, for example).
1479: (Curse of Darkness) Hector and Julia presumably get together after the game ends; he comments upon first meeting her that she looks like his wife. Julia and Hector decide to create a safe-haven for people like Hector; people who have left the path of darkness. This organization is not mentioned again but some people suppose that it is the organization that Genya and 'his associates' who guarded Mina in Dawn of Sorrow belong to.
Incomplete head-canon notes:
Lisa was of noble lineage but her family had been wiped out by sickness. She lived by the waters in the woods near Cordova. Lisa became the closest thing to a doctor most locals could turn to. Upon crossing her path Dracula recognized her as the reincarnation of Elisabetha Cronqvist, and as they had almost 350 years prior, they fell in love and married. Lisa gave birth to Adrian. When Adrian was still young, Cordova was struck by the plague. Lisa's attempts to save the villagers saw her tried and killed as a witch despite the protests of Lyudmil, whose family had been saved by her work and would be subsequently executed for their associations; young Adrian was forced to bear witness to his mother's final words pleading him to show mercy to humans and her burning. The villagers promised him a similar fate for his lineage, but Adrian escaped. Lyudmil was branded a traitor and forced to flee. He sought out Adrian, who had made his way to his father's side, and became Adrian's dear servant in Castlevania.
Beneath Castlevania runs a tributary, called Râul Doamnei (the "Lady's River", the Princess' River). This is for Lisa; the river feeds into the waters of the woods and town she lived and died therein.
During the Dănești clan Vladislav II's rule, Dracula ensorcelled the true Vlad III in order to take advantage of his nobility. In 1456, he took up the rule Vlad had lost, allied with the King of Hungary (Matthias Corvinus, who is actually a servant of Dracula in disguise because before he found Lisa in Wallichia, Dracula WAS Corvinus and he abandoned that position in favor of pursuing her), and had many leading nobles enslaved and slaughtered, giving positions to persons of obscure origins who would be loyal to him (guess what they were). He had two armies, the second being a lesser peasant army. Dracula built a church at Târgșor allegedly in the memory of his false father and older brother who were killed nearby to keep up appearances that he was Vlad III. The Vlad line was against the rival Dănești clan, and they caused trouble for Dracula so he wiped them out, raiding Transylvania for them.
Upon Leon Belmont's questionable victory against the vampire infestation in England in 1094, Matthias Cronqvist found himself bereft of Eternal Night, Bernhard's living castle. The alchemical construct, having been warped by Bernhard's magic, could not maintain form when its master's soul was taken. After Lisa's death, Dracula had the castle reconstructed using enslaved nobles to breathe life back into the broken stone with their suffering as the basis of the binding magic. Thus Castlevania arose, a mighty creature of chaotic magic that reformed at its master's behest. None survived the construction; the slaves that did not die during construction were given to the castle.
When Lyudmil returned to Cordova he found it blighted, and was set upon by a demon. Through the demon's magics, Adrian tainted Lyudmil with vampirism in order to save him, and having found his taste for blood, he returned to his father's side. With his newly acquired power, Dracula let loose his wrath upon Cordova and cursed it.
Dracula instigated war against the Turks and killed tens of thousands of people. Dracula's forces were eventually defeated because his nobles had been alienated by his policies of impalement. He traveled to Hungary and struck a deal with Corvinus, the king. Corvinus had spent money given by the Pope for battle against Turks on other things, and now needed a scapegoat. Dracula had Corvinus place the blame on him, and imprison a doppleganger of Dracula for high treason using false documents claiming Dracula had pledged allegiance to the Turks. Corvinus took great pains to malign 'Vlad's' reputation, and this would work in the vampire's favor, garnering him much support amongst the followers of darkness.
The false confinement lasted twelve years and during that time, being actually free, Dracula solidified his position as a lord of darkness, wreaking havoc wherever he pleased, a blight that none save his evil allies could identify.
Dracula took a second wife at this time, Ilona. Ilona bore Mihnea the Evil, who sought to follow in his father's footsteps but was forced to flee Wallachia. He was killed by assassin Dimitrije Iaxici, a Serbian partisan of the Craiovescu faction. The second, Vlad IV, was unable to lay claim to his father's reign at all. Dracula cared for neither his wife nor his younger children.
It was at this time that Adrian fled his father's side, his eyes opened to his father's evil and his own wrongdoing. He fled Castlevania and took up arms against his father, abandoning his given name. That name, and his origins, would be lost to the obscurity of time, but Alucard would become a legend amongst those who fought in the millenia-long war against the lord of darkness.
On 26 November 1476, Dracula declared his new reign, revealing himself as the shadow that had long haunted the land. He invaded Wallachia. However, his rule ended when Trevor Belmont took up the Vampire Killer bequeathed to him and, alongside Alucard, Sypha Belnades, and the last of the Dănești clan, Grant, who would go on to repair much of the damage done to Wallachia.
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