Spacing - the number of years between children
The sex of each child - and in what sequence males and females are born
Physical, mental, or emotional differences – yes, genes are important
Sibling deaths – which, if occurring early, cause the child below to be “bumped up” to the next birth order
Adoptions – which may or may not have an effect on birth order, depending on how old the child is when adopted
The birth order position of each parent – first-born parents usually run a much different ship than later borns
The relationship between parents – and the parenting style they use as they pass on their personal values to their children
The “critical eye” of a parent – constant criticism takes its toll
The blending of two or more families – due to death or divorce – in a stepfamily certain birth orders often get stepped on