Sarek was born in 2165, the son of Skon. (TOS: "Journey to Babel"; Star Trek III: The Search for Spock; TNG: "Sarek") Sarek was willingly tutored by his own father. (TOS: "Journey to Babel") Sarek's first child, Sybok, was born to a Vulcan princess to whom he was apparently bonded, but not married. (Star Trek V: The Final Frontier)
Some time later, while serving as Ambassador to Earth, Sarek wed his first wife, Amanda Grayson, who gave birth to his second son, Spock, three years later. (TOS: "Journey to Babel"; TAS: "Yesteryear")
Alternate timeline Edit
Officially, Sarek stated that as ambassador, his duty was to study and observe Human behavior and that it was logical for him to marry Amanda to achieve this goal. This was his response when Spock, having been bullied about his own mixed heritage, asked Sarek why he had married Amanda. In actuality, Sarek had fallen in love with her.
Years later, Sarek served on the panel that accepted Spock to the Vulcan Science Academy. When another Vulcan on the panel insulted Spock about his mother, Spock declined the offer of admission. Sarek was shocked, sternly telling his son he had made a commitment to honor the Vulcan way.
Sarek was still on Vulcan when Nero dropped red matter into the planet's core, creating a black hole in the center of the planet. Spock beamed to the surface to rescue Sarek, Amanda, and the rest of the Vulcan Council. Sarek and two other members of the Vulcan Council made it to safety, but Sarek's wife, Amanda, was killed just before they were beamed off the planet. Sarek helped comfort Spock after the death of his mother, saying that he should not try to contain his anger, which he knew was exactly what she would've said in that situation. Recalling his response to the question raised by a bloody-lipped adolescent years earlier – that he thought it logical to marry her – he now told Spock that he did indeed love her. (Star Trek)
Background information Edit
Sarek was played by Ben Cross. He was cast by director J.J. Abrams on the basis of his role in Species – The Awakening. "My agent put me forward for Star Trek," remembered Cross, "and he sent a couple of movies to J.J. [....] There was one particular shot in it where I turned to the camera, and in that moment, it came to him how perfect it would be for me to play Sarek." (Star Trek Magazine issue 145, p. 67)
Despite not being a Trekkie, Cross felt thrilled to play the Sarek character, later reminiscing, "When I realized I was going to be in the movie playing Spock's father, I did feel a certain thrill that I was going to be able to wear those pointy ears." Indeed, his appearance as Sarek involved some extensive hair and makeup, particularly because his scenes in the film Star Trek begin when the character is relatively young and continue as Sarek ages. "My hair and ears could take about two and a half hours to apply," Cross explained. "It was completely painless though – once the ears were on, that was that." (Star Trek Magazine issue 145, p. 67)
To prepare for the role, Cross was sent, from Paramount, samplings of Sarek's previous appearances. (Star Trek Magazine issue 145, p. 67) He also chose to portray Sarek with his own English accent, unlike Mark Lenard's American one.
Ben Cross found that portraying Sarek as initially "cold" and unemotional was not the easiest task. "As Sarek, I had to be true to the Vulcan cultural ethic, which in the beginning, I found very difficult," Cross admitted. "I got a lot of help with that from J.J." (Star Trek Magazine issue 145, pp. 67-68) The father/son dynamic was generally very easy and enjoyable for Cross to participate in performing. He drew on personal experience as a father himself and J.J. Abrams had some additional input into how the actor's performance figured into this aspect of the film. "Of course I got notes from J.J., but if I hadn't played the father/son thing correctly, he would have told me so," stated the performer. "I have a wide emotional range, and one of the things I agreed with J.J. was that if ever I was over the top and strayed into an emotional area – did what would have been quite appropriate as a Human character but as a Vulcan was not – then he would pull me up." (Star Trek Magazine issue 145, p. 68)
Spock actor Zachary Quinto found it was fairly painless to accept Cross as Sarek. "Ben was such a great energy to be around," Quinto remarked. "He has such certitude and a groundedness as Sarek that I was able to connect with him right away." 
In deleted scenes, Sarek and Amanda are seen together, with the newborn Spock. After Spock gets into a fight with bullies, they get into an argument. Following Nero's defeat, Sarek senses Spock Prime's presence.
The birth of Spock is also seen in a flashback in Star Trek V: The Final Frontier, in which Sarek is portrayed by Jonathan Simpson. Since these events (as well as elements of Sarek's backstory, such as his wedding to Amanda) take place prior to Nero's incursion, they logically must take place in both timelines.