Grief is a normal response to the loss of a brother or sister. But adult siblings are sometimes called "forgotten mourners" because their grief is often overshadowed by the grief of other family members, such as the person’s parents, spouse, or children.
Regardless of the type of relationship you had with your sibling, you have the right to grieve. Family members and friends may not understand the role your sibling played in your life. So it is important to communicate to them that you need their support.
A sibling’s death can have many effects on a person, such as:
The loss of a long-term relationship. Siblings are often deeply connected with each other. They have been present in each other’s lives through all of their ups and downs. So their death may represent the loss of a friend, protector, and confidant with whom you share many memories. You may grieve the loss of your past relationship and the role you pictured your brother or sister playing in your future.
Guilt. Sibling relationships can be complicated. They may involve love and affection existing alongside rivalry, jealousy, and arguments. You may feel guilty about things you once said or did. Or you may regret that you did not maintain a closer relationship. You may also replay "what if" and "if only" scenarios in your mind. Or you may experience "survivor guilt," questioning why you were spared, unlike your sibling. Learn more about coping with guilt .
The redefinition of your role in the family. Family members have different, sometimes unspoken, roles and responsibilities that may change when a sibling dies. You may take on new responsibilities, such as becoming the oldest child or an only child to whom family members look for leadership. This change can cause you to feel more stress or resentment during the grieving process.
A fear of developing cancer. Because you and your siblings share many of the same genes, it is normal to worry that you could develop cancer as well. You may also be concerned that other family members will be diagnosed with the disease. Although cancer can run in families, most cancers are sporadic, meaning they occur by chance. Learn more about collecting and sharing your family cancer history .
Tips for coping with the loss of a sibling
Everyone copes differently with the loss of a sibling. There is no “right” way to work through your feelings of grief and no specific amount of time it takes to recover from those feelings. The following tips may help you throughout the grieving process:
Share your grief with other family members. Your entire family is grieving the loss of your brother or sister. But each person grieves in his or her own way. Talking about your shared grief can help you work through your pain and sadness together.
Find support outside your family. It can be helpful to seek support from your family. But it can also be hard for some family members to provide consolation while coping with their own grief. Consider talking about your loss with people outside your family, such as a close friend, a clergy member, or a grief counselor. Support groups  can also provide a setting to talk with others who share and understand your experiences and feelings.
Forgive yourself. Siblings compete, argue, and challenge each other. Forgive yourself for any unkind things you did or said or for things you wish you had done or said but did not. Forgive yourself for not maintaining a close enough relationship with your sibling. It does not mean you did not love him or her.
Take care of your physical health. Help ease some of your fear about your personal cancer risk  by focusing on developing and maintaining a healthy lifestyle. Have regular checkups and get medical tests as recommended by your doctor. Compile your family's cancer history and share it with your doctor and other family members.
Take care of your mental health. Feeling extremely sad or numb are normal reactions to the loss of a sibling. But sometimes these and other symptoms of depression do not lessen over time, and feelings of hopelessness, anxiety , or anger can begin to affect your daily life. If you feel this way about your grief, ask your doctor about grief therapy. Depression  related to grief can sometimes be treated with medication.
Find ways to remember your sibling. As the pain of grief begins to ease, it may feel like you are beginning to forget your sibling. Finding ways to memorialize your brother or sister can help keep his or her memory alive and maintain a feeling of connection. You may decide to make a family memory book with pictures, stories, or other mementoes contributed by different family members. Or consider volunteering with a cancer-related charity or one that was important to your sibling. Read more about ways to cope with grief .
Parenting a child who has lost a sibling
The death of a sibling is a tremendous loss for a child. However, parents are often preoccupied with their own grief and overlook the needs of grieving siblings. A surviving child may feel the need to "fill in" for the deceased child or may worry that you would have preferred if he or she had died rather than the sibling. It is important for parents to recognize the grief of surviving siblings and to support them.
Learn more about how parents can help children cope when a sibling has cancer  and how to help a child or teenager who is grieving .
The Compassionate Friends: Grief Support for Siblings 
National Cancer Institute: Grief, Bereavement, and Coping with Loss (PDQ®)