pen name: whereiswaldo Having siblings can affect attachment with the parent. The older child may not form an appropriate attachment with the parent if the younger child is born very soon after. However, I would also argue that having siblings can help the attachment especially in a family where both parents work. Younger child who has an older sibling may form some type of secure attachment with the older child if the both parents are not around as much. In this case, the old child would have to be somewhat more older than the younger child (e.g. if two siblings are only a year apart, the attachment is unlikely). In contrast, if you are an only child, the child may form more of Anxious/ Resistant attachment or Anxious/ Avoidant attachment than a child with siblings if both parents are not around as much.