second child syndrome

when i was in maktab long time ago, my lecturer had told us the story about this syndrome.  it is called second child syndrome and basically it refer to sibling with same sex in a row, for example the first and second daughter, the first and second son, or the third and fourth daughter and so on. Here is the hypothesis is all about: if you have 2 daughters in a row,  normally the second one would be much much extra in every way.  it is either lebih nakal, lebih garang, lebih keras hati, lebih daya tahan, lebih malas, lebih pandai, lebih suka merajuk, lebih manja or anything compared to the first one.
i dont know how true the syndrome is but when i checked on the net, there is other version of  meaning of the syndrome.  Though it just an opinion based on incomplete evidence, i do feel the truth of it anyway.  If i look in my families, among our cousins the second child is more  mischievous, stubborn, daring and enthusiastic. The closest example is my daughters.  When Dada was small, she didn't bother to play with my vase or glassware or any other thing that i put on the shelf or locker and our home at that time can be considered well organized.  But when it come to Ari ,everything turn to helter-skelter!