All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
This is one of the serious new issues that contemporary scholars have researched and investigated, and their conclusion was included in Dr. ‘Umar Al-Ashqar’s book Qadhaaya Tibiyyah Mu‘aasirah (Contemporary Medical Issues). It says that the researchers of this issue reached two different opinions:
The first group is of the opinion that the real mother to whom the child should be attributed and who is entitled to inherit (from the child) is the one who produced the egg (ovum), while the surrogate mother who rented out her womb and bore the child and gave birth to it is like a breastfeeding mother. She is thus a virtual mother, meaning that we hold her in the same status of a mother by virtue of her providing gestation and nourishment for the child, but the child is not attributed to her, and only the breastfeeding relations are affirmed for her. He then mentioned the evidence provided by those who held this view.
The second group is of the view that the real mother, who is entitled to inherit, is the one who possesses the womb (surrogate mother) and carried the child and gave birth to it, while the mother who provided the egg is the virtual mother, like a breastfeeding mother … The research concluded that the view of the first group is the preponderant one – that the (biological) mother who provided the egg is the real mother and that all the rulings pertaining to inheritance, financial maintenance, custody, etc. are affirmed with respect to her, and this is by virtue of the egg and because the child inherits all its genetic traits from her.
The issue is open to Ijtihaad (scholarly reasoning), and there is nothing wrong, Allah willing, with opting for the opinion concluded by the research and held to be preponderant. Accordingly, all the Sharee‘ah provisions related to family relations apply to these children; you should treat them just as you treat your other children who were born naturally.
They should not be informed of how they were born, nor should the rest of your children be informed of it because this may be a source of inconvenience for them.
Allah Know best.