I am my parents only child, no siblings, either biological or adopted.
hmmmm....does that have any freaky side effects?
It relates to applied only to those individuals who have never had siblings
right, but what effect has that had on you as a person?
Well,I wish I had a Siblings play a unique role in one another’s lives that simulates the companionship of parents 
uh huh. so being an only child has made you a little off, huh? haha
Some children may have half-siblings or step-siblings, either living at the same house 
well I hope you find your metaphorical brother or sister someday! everybody deserves to have a sibling!
Sibling relationship
Siblings play a unique role in one another’s lives that simulates the companionship of parents as well as the influence and assistance of friends. Because siblings often grow up in the same household, they have a large amount of exposure to one another, like other members of the immediate family. However, though a sibling relationship can have both hierarchical and reciprocal elements, this relationship tends to be more egalitarian and symmetrical than with family members of other generations. Furthermore, sibling relationships often reflect the overall condition of cohesiveness
Only child
An only child is a person with no siblings, either biological or adopted. 
Children who have half-siblings or step-siblings, either living at the same house or a different house - especially those who were born considerably later - may have a similar family environment to only children, as may children who have much younger siblings from both of the same parents (generally ten or more years).
Overview.
Throughout history, only children were relatively uncommon. From around the middle of the