No, it is not common nor considered socially acceptable for an older sibling to fall in love with their younger sibling, or vice versa. Such feelings would be categorized as "incestuous" and are widely regarded as taboo in virtually all cultures and societies.
Incest refers to sexual or romantic relationships between family members who are closely related by blood or marriage. The harmful consequences of incestuous relationships are well-documented, and most societies have strict laws and social norms in place to prevent and condemn such behavior.
Healthy sibling relationships are based on mutual love, support, and care for each other as family members. The idea of romantic or sexual feelings between siblings is considered abnormal and psychologically troubling. These feelings can arise due to complex psychological factors, but it is crucial to address and seek professional help to manage such emotions appropriately.
If someone is experiencing confusing or inappropriate feelings towards a sibling, it is essential for them to seek counseling or therapy from a mental health professional. Talking to a qualified therapist can help them understand and cope with these emotions in a safe and responsible manner.
Remember, it is crucial to prioritize the well-being and safety of all family members and to uphold the boundaries and norms that promote healthy family relationships.