Have you been up against your sibling?
Ed Miliband has praised his brother David's "generosity and graciousness", after defeating him in the Labour leadership race. Have you worked or competed against a sibling?
There is now speculation he may be offered the shadow chancellor's role, but he is also said to considering whether to quit politics.
This is not the first time sibling rivalry has been in the public eye, tennis champion Venus Williams has also suffered defeat at the hands of her younger sister on court.
Some siblings, such as former Oasis members Liam and Noel Gallagher, have failed to hide their rivalry, whereas Minogue sisters Dannii and Kylie have both forged successful pop and soap star careers.
What are your experiences of sibling rivalry? How did you cope? Do you have a positive experience of working or competing with a sibling? What advise would you give?
Thank you for your comments. This debate is now closed.