As the prophecy spoke: In the year 1999, the Belmont clan returned to reclaim the Vampire Killer and the mystic weapons. It was Julius Belmont who took possession of his family's heirlooms. By this time, vampire hunters finally had the answer: If they could not defeat Count Dracula once and for all, then they would instead have to stop this eternal cycle by finding a way to permanently contain the Dark Lord. It was Julius who was their leader in this endeavor. Julius ventured into the Count's feared castle and made true his birthright, defeating Dracula in a duel; then by combining his powers with the incantations of the Hakuba Shrine priests, the group was able to seal away Dracula's powers, his dreaded castle, and its multitude of lurking demons within the darkness of a solar eclipse, where it seemed they would forever be locked away.
This act of supreme power not only sealed away Vlad Tepes Dracula and forever removed at least him as a threat--for Julius, it proved to be a traumatic experience that robbed him of his memory and threatened to leave him a lifelong amnesiac. With the Church going out of its way to cover up the event, the legacy of his family, too, was in danger of being forever locked away in myth. So thirty-six years later, when the seal threatened to break (with Dracula's power sure to leak out, seeking to become reborn within a new suitor), it's no surprise that Alucard rose from his grave to assess what would be a Belmont-less scenario. In order to blend in with a society that had long since evolved, Alucard, his appearance cold, easily became a member of a shadowy sect of Japanese National Security under the name "Genya Arikado." From this position, he could investigate the source of the leaking power and its relationship to the Hakuba Shrine in Japan; he joined together with someone who would prove to be a familiar ally--Yoko Belnades, a descendant of Sypha, who he fought beside over five hundred years before--so that they could work together to find a way to enter the castle.
"Belnades?" you ask. "But what happened to 'Fernandez'?" There's no explanation for this storyline-wise, but frequent contributor Carl Savorelli argues correctly that the names are one in the same, both roughly translated using the Japanese dialect (one of three alphabets, in this case) of "katakana," which they use to write foreign words in a more simple fashion. Because the system lacks a way to interpret certain letters, translators are forced to sometimes improvise during localization. In the case of Castlevania 64, for instance, a localization team could have easily taken "Verunandesu" and translated it into Bel-na-des where the Japanese crew had Fer-nan-dez. Another explanation is that our good friend Koji Igarashi, while accepting Castlevania 64 as part of the official timeline, can easily change his mind and at any time disqualify it (which would make things very messy for both this section and the website as a whole), which would mean that the name "Belnades" was never actually lost.
But threatening to be reborn into this world was a new Dark Lord. Alucard knew the deal: The dreaded Castlevania and its many demons shared with their Lord a symbiotic bond; in actuality, all such respective entities existed within and subsisted upon the force of their own realm (which to the shock of at least the player is a place having no actual tie to Europe), which they inhabited merely as Dracula's possessions. Together, this trinity of essences represented the embodiment of the "Dark Lord." To combat this event, Alucard would have to put into action a flawed plan whose risks because of the immediacy would have to be ignored. He'd have to (a) find a man with powers one in the same but of a good heart, (b) magically transport him into the castle on the day of a solar eclipse in 2035, and (c) manipulate him into using his natural absorbing ability to steal the demon and castle essences; thus, such a specimen would then be able to trick the chaotic forces into believing this to be their Dark Lord and then sneak into an area where "only Dracula could go," the Chaotic Realm where the seal lay broken, its contained energy leaking. That "someone" was Soma Cruz, a naive young man who thought of himself as nothing but ordinary. During his adventure, as he began realizing his true self, he grew in power; it was only a matter of time before he was able to absorb the abilities of every creature in sight and become a true pseudo-representation of Dracula. Therein, he was able to enter the Chaotic Realm and complete the task, closing the seal and thereby ridding himself of the possession of demon souls. In the end, Alucard was successful in bringing out Soma's suppressed determination and transforming an ordinary young student into yet another hero of legend.
Soma was a hero, that is, who through this very process was now susceptible, as Alucard knew well. By tasting the enormous power possessed by one such as Dracula, it would remain as more than just a memory, for somewhere within him lay sleeping Dracula's power, which he would forever have to control in order to prevent his own transformation into the true Dark Lord.
More importantly, Soma's meetings with the amnesia-suffering Julius, who found himself wandering the castle under the name "J," returned to the Belmont his senses through a series of encounters (one violent) and thus saved the family's lineage. It was Julius' sensing of Soma's "dark power" that made something click--it was Soma's Dracula-like presentation that allowed his mind to reset and remember who he truly was. Alucard's was a dangerous and potentially disastrous plan, but it worked to prevent the return of ultimate evil--at least in a sense. Though it seemed that the order was repaired, there was left an imbalance; because of the absence of a true Dark Lord, whose spirit was suppressed within Soma, evil forces would naturally react by attempting to goad Soma into realizing his "true" potential and thus become their new Dark Lord. Other possible candidates would surely harbor that dark power and try to wrest it away from its uninterested wielder.
It would be up to Soma to decide which path to take in combating against their plotting. He at least had a fail-safe: It was Julius Belmont who promised to fulfill his destiny should Soma ever choose the wrong path and succumb. (Perhaps hinting at his future propensity is his Japanese name "Soma Kurusu," whose separate parts, as translated by reader Solar Boy, together reveal a clear purpose; Soma is "pale/blue plus truth," while Kurusu is "coming plus necessary.")
A lot of what you've just read is part conjecture and sometimes pure speculation, and there is a lot more that will be added over time. But when you put it all together, Julius Belmont, for now, is the pinnacle of this cursed bloodline. Belmont, Belnades, Alucard, Renard, Fernandez, Morris--no matter what you call them, no matter how much the names have changed, these are the heroes of Castlevania. And the past is still waiting to be written.