Niklaus Mikaelson
The relationship between Klaus and Rebekah. They're half-siblings and were the closest pair out of their family.
Family Bond, Klaus gives his child into Rebekah's care, assured that she will be able to love, care, and protect his child. Klaus bears no ill will to his half-sister and genuinely wishes her happiness.
Elijah Mikaelson
The brother-sister relationship between Original Vampires Elijah and Rebekah. Elijah and Rebekah share a close relationship as brother and sister. According to Elijah, he got along well with all his family, especially his younger sister Rebekah.
It is shown that Elijah and Rebekah have a particularly close relationship. He revived her along with their brothers, Kol and Finn, in Bringing Out The Dead. Elijah seemed to trust Rebekah most out of all his siblings and has a particularly soft spot for her (probably because she is his only sister). He confides in her in All My Children about his suspicions on their mother's intentions. Rebekah seems to look up to Elijah, giving him more respect than any other of her siblings and looking at him for leadership during some tough situations. They also comforted each other after they believed that their half-brother Klaus was dead. When Rebekah was in jeopardy in Eva's body, Elijah swore to never abandon his sister. Today, they are very close and would do anything to protect each other. Elijah and Rebekah always show concern about each other's happiness.
Hope Mikaelson
Rebekah is the paternal aunt of Hope, the daughter of Niklaus Mikaelson and Hayley Marshall. Hope's parentage and unique status as a living hybrid made her an ideal target for exploitation or sacrifice by numerous adversaries even before she was born. Rebekah, whose relationship with Klaus (or Nik as she calls him) had been strained for centuries, had left New Orleans not long before Hope was born to start a new life for herself.
By the time Hope was born, the supernatural situation in the city had deteriorated to the point of all-out war between the Original Vampires, non-original vampires, witches, werewolves and mortal factions. Hope's parents along with Elijah, her paternal uncle, knew that she would be under constant threat from these enemies. Wanting a happy life for their daughter, Hayley and Klaus concluded that it would be best if she was not raised in the embattled city. The first step to achieving this goal was to convince the world that their newborn child had died on the day she was born. In order to ensure Hope's safety, Klaus then called upon Rebekah - who, despite their troubled history, he trusted above all others - to take and raise his daughter in secret, far away from those that would see her dead. She gladly did so, promising Klaus that Hope would be happy.
Kol Mikaelson
Kol is the older brother of Rebekah. He seems to be a year or two older than her. Since Henrik died, they are the youngest Mikaelson siblings. It is seen that Kol and Rebekah are partners in crime whenever they have been on screen together. Mostly it is Rebekah who in charge and Kol who does the dirty work for her. He could be considered her 'henchman' and doesn't seem to mind whenever she calls him to help her. He is always there for his sister, despite their differences. Kol is protective of Rebekah as it is seen that he even stands up against Klaus to defend her, though he never says that out loud.
Rebekah seems to know Kol better than anyone. She can tell when he is being sincere and knows what he enjoyed as a human, such as his favorite holidays.
Like Klaus, Kol does not like any of Rebekah's lovers and seems to dismiss them whenever he comes into contact with them, especially Damon, Marcel and Matt. Though he already hated Marcel for taking his place in the family.
Rebekah and Kol bicker constantly, mostly because they are the closest in age, and Kol has made fun of her love life, but despite that, it is shown that they do love each other and are protective of one another. Rebekah mourned Kol after he died but didn't avenge him, which upset Kol greatly and he did resent her, especially when she betrayed him 100 years before. He punished her for her selling him out 100 years prior by putting Rebekah in another body and imprisoning her in the Dowager Fauline Cottage.
Rebekah says that Kol is her brother and she have loved him many lifetimes longer than Davina have been on this earth. She will stop at nothing to get Kol back, no matter what flesh she in.
Freya Mikaelson
Freya is the older (and only) sister of Rebekah Mikaelson. Rebekah first meet her sister in 1914 at a Christmas party Freya knew who she was but Rebekah had no know idea that she was talking to her keen. The two sister's reunited in the Dowager Fauline Cottage Freya helped Rebekah when she was stuck in the cottage, It was there that Rebekah learnt that she has meet her long lost sister Freya.
Finn Mikaelson
The strained relationship between Original vampire siblings Rebekah and Finn. The two siblings do not share a close relationship, partly due to the fact that they were not able to spend much time together while Finn was incapacitated by a silver dagger for nearly 900 years and dead for several years after he was awakened, and partly due to the fact that Rebekah has tended to side with their brother Klaus. Finn and Rebekah have not physically interacted since The Murder of One.
EstherMikaelson
Not much is known about this relationship. Rebekah spent most of her centuries-long life believing that her mother was killed by Mikael. However, in Season 3, Elena discovered the truth when she was examining the Mikaelson family's cave drawings - Esther was actually killed by Klaus. Upon Esther's first return to life after her original death, Rebekah was shown to care deeply for her mother and refused to believe that Esther wanted to kill all of her children. When she found out about Esther's true plans, her feelings changed to anger and resentment, especially after Esther hijacked her body to further her plans to kill her and her siblings.
Mikael Mikaelson
The father - daughter relationship between Mikael and Rebekah Mikaelson. They are enemies, and she hates him for what he did not only to her, but her brothers. Rebekah is one Mikael's favorite children.
Marcel Gerard
Rbekah and Marcel have a passionate forbidden love. When they are in the same room, it's like electricity, it's both emotional and physical with them. Although both of them have betrayed the other, they still love each other.
Hayley Marshall
They met in New Orleans when Rebekah came to find Elijah. Even if she first said that she didn't care about Hayley and her baby - who is her niece it clearly appeared that she did, watching over Hayley many times. Later when Hayley gave birth to her daughter Hope, she decided to give her temporally to Rebekah to keep her safe.