Physical discipline, such as popping a newborn on the butt, is generally not recommended and could be considered abusive. Infants are very delicate and vulnerable, and using physical force on them can cause harm and distress. Physical discipline can also lead to negative psychological effects on the child.
In many countries, physical discipline of children is legally restricted or even prohibited. Instead, experts recommend positive and non-violent methods of parenting, such as nurturing, comforting, and responding to a child's needs with love and care.
If you are concerned about your brother's well-being or any potential abuse, it is essential to discuss this with a trusted adult, such as another family member, teacher, counselor, or a child protective services professional. They can help assess the situation and take appropriate actions if necessary to ensure the safety and well-being of the child.