The soul meets the pitrukkal (ancestors soul) in the house of manes. it goes through a review. it is said that the soul goes through a training program or observation until ready to take a shape. the soul agree to cleanse the part of the karma it has done in the past and wait for the right time to take a shape. when the time strikes, it enter into the womb of the mother. it is also said that between 3 to 4 months of the development of the foetus is when the atman(soul) enters the body of the child. The soul takes the shape when the planetary cobinations are in perfect harmony with its prarabda karma it has agreed to cleanse. hence as per the agreement the right womb is chosen, there by father, mother, family , environment etc. what ever happens after the birth would be in perfect harmony with the prarabda karma of the soul. Here one may wonder what is the real connection between this kid and the mother, father etc. it is true that there is no real link, they are different souls all together but for the cleansing purpose biologically they are linked together. this is a beautifully written program that never fails.
Om Tat Sat