Throughout the centuries Dracula often gets lonely so he choose 3 women to serve and provide him with undead companionship.
From the Novel
In the original story of Dracula, the Brides are first seen when Harker stumbles into their chambers and falls asleep, unaware of their presence until the three approach him and try to drain his blood. Dracula stops them before they get the chance, citing he forbade them not to touch Haker as he still needs him to complete his business transaction to London. The brides chide back that Dracula "never loved" (implying that he never loved them) but he just snaps back that their existence is proof of their "love". To appease the women, he promises to give them Harker once he's through with him and in the meantime, gives the three a "wiggling bag" to sustain them for the night. The contents of the bag are never shown but it's implied to be a baby. Harker, somewhat half asleep through all of this, makes to escape the following day. It's implied through his delirium as he escaped from the castle that the brides tried to chase him but were unable to catch him.
They are not seen again till the end of the novel when the protagonists are tracking down Dracula to kill him before Mina turns into a vampire. Van Helsing and Mina split off from the others to take a separate route to Dracula's castle. As they get near and make a camp for the night, the brides suddenly appear having sensed the growing transformation in Mina. They beckon her to come with them calling her "their sister". Helsing however counteract their influence by placing holy wafers on the ground around Mina, allowing her to keep her sense of self. The brides however continue to try to claim Mina, at one point killing and feeding on their horses. Eventually the sun rises and the brides are forced to flee back to their castle. Helsing, after securing Mina, goes to the castle and tracks down their sleeping quarter before staking all three of them.
Tomb of Dracula
In the Marvel version of the story the brides are named Bettina, Catherine, and Velanna. Along with appearing in the original story, they appear in the Dracula Lives story, Ghost of a Chance (Presumably set before the events of the novel). At the beginning they see Dracula brooding and try to pleasure him (even wagering which one he would pick). He rejects them, stating to himself that they are impure and were nothing more then winches he had take off the streets and transformed.
Through the Tomb of Dracula series, Dracula has a number of women he makes into his brides either from his earlier ancient time to some of the modern era, including a few of the protagonists who have hunted him. Most of the time they obey him without question and serve as obstacles to the heroes. Even aiding in Dracula's resurrection a few times.
Though of course as minor characters they never last long and will usually be killed by the end of the issue or at most never seen again.
The most prominent story that really focuses on them in the series is the two part story arc, Pit of Death (issue #7 and 8), in which the protagonist, Lupescu, falls into a trapdoor while invading Dracula's castle. He slides into a water way dungeon where coffins are stored nearby. No sooner then he arrives, the coffin opens and Dracula's numerous brides arises to attack him. Among which is his blind wife, Velanna, whom Dracula turned in retaliation for Lupescu trying to rile the town to attack him. Lupescu manages to find his cross in the water way and uses it to ward off the brides, weakening them enough that he can stake each one. Though Lupescu dies at the hands of Dracula, he comes out the victor as he arranged the bodies of the women into a cross so that Dracula can't remove the stake in their bodies to revive them.
Victorian Undead II: Sherlock Holmes vs Dracula
The brides are first seen in Issue 3 of the mini-series where Harker tells Sherlock Holmes of his encounter with them during his stay in Castle Dracula. At the end of the issue, when Holmes, Watson, Seward, Helsing, Quincy and Harker raid what they think is Dracula's hideout, they only find empty coffins. Unaware that the brides along with a vampire-ized Lucy Westerna are above them waiting to ambush them. They attack in issue 4 where one manages to grab and kill Dr. Seward. The heroes retaliate with Quincy beheading one bride, Holmes shooting a flare into another and Lucy, finding herself becoming outnumbered despite her resistance to their crosses, killing the last bride in exchange for the men letting her go.