Of all the father-son relationships in Star Trek, the relationship between Sarek (Mark Lenard) and Spock (Leonard Nimoy) is the most tragic. When he's first introduced in Star Trek: The Original Series season 2, episode 15, "Journey to Babel", Sarek had been estranged from his son Spock for 18 years. After Spock saved Sarek's life, father and son eventually reconciled their differences. However, it was later revealed in Star Trek: The Next Generation that political differences had separated them once again.
Interestingly, Star Trek: Discovery season 1 revealed that Sarek (James Frain) had raised Commander Michael Burnham (Sonequa Martin-Green) and was very close to her, posing the question of why raising a Human as a Vulcan was easier for Sarek than raising a half-Human, half-Vulcan child. Fathers and sons are important in Star Trek, from the fatherless Wesley Crusher (Wil Wheaton) in TNG to Will Riker (Jonathan Frakes) and his disapproving father Kyle (Mitchell Ryan), to Jean-Luc Picard (Patrick Stewart) confronting his traumatic childhood in Star Trek: Picard season 2. However, they all made peace with their absent or difficult fathers, but Spock didn't get the chance.
