What is effect of birth order on interpersonal relationships?

Answer 1

Stereotypically,

First children tend to dominate

Last children tend to be spoiled

Middle children tend to get less attention

So...

Relationships work better if the partners are not both first or last children. In general, a mix works better.

But it is certainly not a relationship-breaker if they are both the same status

Answer 2

Generally speaking birth order directly effects a person's personality traits, not only in adolescence, but throughout a person's life. Frank Sulloway has done some amazing research and has come up with five major personality traits that are affected by birth order. They are:

1. Openness to experience - first borns tend to be more intellectual whereas latter-borns tend to be more adventurous and rebellious.

2. Conscientiousness - first borns tend to be conscientious than latter borns.

3. Extroversion - first borns tend to be more socially dominant and later borns tend to be more social.

4. Agreeableness - Later borns tend to be more agreeable than first borns

5. Neuroticism - There are modest differences here, later borns tend to be slightly more neurotic than first borns.

It is important to remember that this resets if there is a gap of 7 years or more in between siblings and single children overwhelmingly identify with first borns.

It is also important to remember that there are no hard and fast rules when it comes to individuals and their personality traits. There are countless exceptions to each of the above observations.