All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
The child follows his parent, if both of them or one of them is Muslim then the child is Muslim, and there is no need to order him to declare the two testimonies of faith when he reaches the age of puberty, but if his parents are non-Muslims, then there is a need for this.
An-Nawawi said: 'Every new-born child is born while being prepared to accept Islam, so if both of his parents are Muslims or one of them, then he continues on Islam with regard to the rulings of the Hereafter, but if both of his parents are non-Muslims, then the rulings that apply to his parents in this life will be applied to him.'
Allaah Knows best.