Another factor that could affect attachment is siblings in the house. If another child, for instance, is born very soon after the first child, the parents attention may shift to the younger child and the older one may not have the proper time to connect with the parent and feel attached. Also, if there are sick family members or siblings in the house while the child is developing, much attention may be deferred from them and they therefore wont have the time to develop the security and trust needed for a secure attachment
I agree with Norbert, that siblings can affect attachment. The older child may not form appropriate attachment with the parent if the younger child is born very soon after. However, I would also argue that having siblings can enhance 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 contrast, if you are an only child, the child may form more of Anxious/ Resistant attachment or Anxious/ Avoidant attachment.
I agree that siblings is a contributing factor. However, I do not think it contributes to more insecure attachments. As a twin, I have always had to share my parents. I think that it allowed me to form extremely secure attachments with my parents. My parents understood that it was not easy for my sister and I to have to share everything growing up. So, they always tried to give us each "alone time" and tried their hardest not to give one more attention then the other. This allowed me to use every bit of the time I had with them to truly bond. Additionally, I learned very quickly that sometimes my parents needed to focus on my sister. While this was a hard concept sometimes, I knew that they would try to make up for it later and that just because they needed to pay attention to my sister didn't mean they weren't ever going to pay any attention to me.
