This is a list of mentions of brothers and sisters in the Lost mythos.
- Charlie and Liam Pace
- Eko and Yemi Tunde
- Hurley and Diego Reyes
- Chris and Steve Dobson
- Faith and Gayle Harrington
- Janelle and Unnamed Sibling
- Sally and Sandra Rafflethorpe
- Emma and Zach
- Jacob and The Man in Black
- Juliet and Rachel Carlson
- Carole and Lindsey
- Charlotte and two younger sisters
- Desmond and three brothers
- Lisa and Joanne Gellhorn
- Boone and Shannon (step-siblings)
- Jack and Claire (half-siblings)
- Daniel and Penny (half-siblings)
- Locke, Jeannie and unnamed male (foster siblings)
Charlie and Liam Pace
Charlie and Liam Pace are both members of the band Drive Shaft. Liam is the older brother and lead singer of Drive Shaft, which sometimes leads to arguments between the brothers. Because of Liam's big influence on Charlie, he starts to take drugs just like his big brother. Their relationship is normal: they fight sometimes but actually they love each other. Charlie went to Australia to see Liam and talk to him about the band. His flight back was Oceanic 815.
Eko and Yemi Tunde
Emma and Zach
Emma and Zach were on Flight 815. On the survivors' 12th day on the Island, the Others took Zach and Emma with them. There they live now and seem to have everything they need. Zach and Emma where on the plane because their mother lives in L.A..
Juliet Burke and Rachel Carlson
Juliet Burke and Rachel Carlson were very close. Rachel's chemotherapy made her steril but Juliet secretly treated her and Rachel got pregnant. Shortly after Rachel told her, Juliet was offered a job on the Island. She agreed to work for Ben and the Others for 6 months because she wanted to be back before her sister would give birth. Ben prevented her from going back by saying Rachel's cancer had come back and she and the baby would die unless Juliet stayed. Later he showed her a video of Rachel and her son Julian. Rachel named her son Julian after her sister, who helped her getting pregnant.
Boone and Shannon
When Boone was 10 and Shannon was 8 his mother and her father got married. Later Boone fell in love with his step-sister, which she knew about although he had never really told her. In Sydney they spent the night together in a hotel room and had sex. Boone seemed to think that their relationship would change after that but Shannon told him it would never happen again and they would just be brother and sister.
Jack and Claire
Jack and Claire have the same father, Christian Shepard. Claire never met her father until he decided to pay for Carole Littleton's hospitalization. Even then he didn't tell Claire his name because she said she didn't want him to. Therefore it is rather unlikely for Jack and Claire to find out about their relationship on the Island. In a flashforward, however, we see Carole Littleton at Christian Shepard's funeral. She tells Jack about her affair with his father and their daughter, Claire, causing Jack to finally realise his relation to Claire. Claire herself learned of this sometime during the three years she spent alone on the Island, as, upon Jack's return, she greeted him as "my brother".
- Desmond refers to most of the men he speaks to as "brother". Furthermore, he briefly mentioned having to look after his brothers after something occurred involving their father. Also, he briefly attended a monastery where the members addressed each other as "brother".
- Ben drew the map to the balloon on the title page of the novel The Brothers Karamazov.
- The song Brothers by Drive Shaft, as composed by Charlie on the piano in "Fire + Water"
- Naomi's last words before dying are "Tell my sister I love her", which turns out to be a code for being under duress.