In May 1750 another girl was born, and again died young, this time at eleven weeks." 1
That time Leopold was organizing the publication of his musical instruction dissertation Violinschule together with Johann Jakob Lotter, a friend and printer in his home town of Augsburg. He wrote about the good event to Lotter in a letter of February 9: ". . . I must inform [you] that on 27 January, at 8 p.m., my dear wife was happily delivered of a boy; but the placenta had to be removed. She was therefore astonishingly weak. Now, however (God be praised) both child and mother are well. She sends her regards to you both. The boy is called Joannes Chrisostomos, Wolfgang, Gotlieb."
There is not very much information about Wolfgang's very early life available. Almost certainly, his father focused on his court career and on giving lessons. Surely he taught Maria Anna, who was called Nannerl in the family. When she was seven, Leopold started teaching her to play the clavier -- and quickly discovered to his real pleasure that she had a talent for music. He continued to teach her, attracting her with a number of exercises that he created for her in a notebook that he called Pour le clavecin, ce Livre appartient Mademoiselle Marie-Anne Mozartin 1759.
The boy's inquisitiveness was fired up as well. ...