How many pairs of episodes do you think are brother and sister episodes, shows whose title, plot, and/or content are similar in unique ways? I have a few.
1) The Shape of things to come & Dead is Dead: both focus on Ben, most notably his rivalry with Charles Widmore and his relationship to Alex. Both show Alex's death and Ben trying to summon the smoke monster. Both involve Locke (well, Terry O'Quinn) as the one who is very coercive in bringing Ben and another 815 passenger to somewhere very important on the island, and both include Ben's plan to kill Penny.
2) The Man behind The Curtain and Cabin Fever: Both focus on the two leaders of the island and reveal the similarities between them- both were born prematurely to a mother named Emily and were chosen by the island at a young age. Both involve meeting Richard at a young age. Both include Horace, mention what happened in the purge, and show the Dharma grave. Both involve Locke and Ben going to see Jacob's cabin.
3) The Constant and The Variable: Both center around time-travel and the inter-connectedness between Desmond and Daniel. Both deal with conquering the negative effect of time-travel through human emotion. Both include Daniels book and its importance. Both feature the love between Desmond and Penny
4) Man of Science, Man of faith and A tale of two cities: Both center around Jack flashbacks to particular moments with Sarah. Both open consecutive seasons and do so with a suprising twist involving a future important character. Both involve Jack facing his two greatest rivals in emotionally packed moments (Locke and Ben).