Sleeping with siblings, whether intentionally or unintentionally, is called incest. Incest is a term used to describe sexual activity between family members who are too closely related to each other. This includes sexual contact between siblings, as well as between parents and children, and other close family members such as cousins or grandparents.

Incest is considered taboo in many cultures and is illegal in most countries. The reasons for this are multifaceted, but generally, incest is seen as a violation of social norms and a potential threat to the genetic health of future offspring. Incestuous relationships can lead to genetic abnormalities, which can result in physical or developmental disabilities in children. Additionally, incest can cause emotional harm and trauma, especially when it involves abuse or coercion.
Incest is generally viewed as a form of sexual abuse, especially when it involves minors or individuals who are not able to give informed consent. This is because incest often involves a power imbalance between family members, which can make it difficult for individuals to say no or to resist sexual advances from a family member.
There are a number of factors that can contribute to the occurrence of incest within families. These may include family dysfunction or conflict, sexual abuse within the family, mental illness, substance abuse, and social isolation. However, it is important to note that incest is never acceptable or justified, regardless of the circumstances.
If you or someone you know is experiencing sexual abuse or incest, it is important to seek help from a qualified professional. This may include a therapist, counselor, or social worker, who can provide support and resources for healing and recovery. Additionally, there are a number of organizations and hotlines that specialize in helping individuals who have experienced incest or sexual abuse. These resources can provide information, support, and referrals to appropriate services and resources.