Who has Parental Responsibility?
By virtue of The Children Act 1989 s.2(1) and s.2(2), the mother
of a child will always have Parental Responsibility for the child automatically on the birth of that child, whether she is married to the father at the time of birth or not. Fathers, grandparents, step-parents, "second female parents" and others can acquire Parental Responsibility, in a number of ways.
Aquisition of Parental Responsibility by the Father
The Children Act 1989 s.4(1) sets out the circumstances when a biological father of a child will acquire Parental Responsibility. The father
of a child will only acquire Parental Responsibility if he:
is married to the mother at the time the child is born;
is not married to the mother at the time of birth but he is registered on the birth certificate as the father;
he enters into a Parental Responsibility agreement with the mother;
the court makes a Parental Responsibility Order under s.4 Children Act 1989.
Acquisition of Parental Responsibility by Step-Parents
The Children Act 1989 s.4A(1) states that: "(1) Where a child's parent ("Parent A") who has Parental Responsibility for the child is married to, or a civil partner of, a person who is not the child's parent ("the step-parent")-
(a) parent A or, if the other parent of the child also has Parental Responsibility for the child, both parents may by agreement with the step-parent provide for the step-parent to have Parental Responsibility for the child; or
(b) the court may, on the application of the step-parent order that the step-parent shall have Parental Responsibility for the child."
So in summary, a step-parent can acquire Parental Responsibility for a child either:
by agreement of those parents who have Parental Responsibility for the child; or
by order of the court.
Can Other People Acquire Parental Responsibility?
The Children Act 1989 s.12(2) states that:
"Where the court makes a Residence Order in favour of any person who is not the parent or guardian of the child concerned that person shall have Parental Responsibility for the child while the Residence Order remains in force."
An example of this might be when the grandparents of a child want to care full-time for him because his own parents suffer from a serious illness. In those circumstances the grandparents could apply to the court for a Residence Order under The Children Act 1989 s.8. They would automatically acquire Parental Responsibility on the making of that Residence Order.
The same is true in the case of Shared Residence Orders
. For example, the mother and biological father of a child may have separated. The mother may be living with her new boyfriend to whom she is not married and who is no relation to her child. If the court was satisfied that the new boyfriend had played enough of a part in the child's life and that it was in the best interests of the child for the mother and the new boyfriend to share residence of the child, the new boyfriend would automatically acquire Parental Responsibility for the child under The Children Act 1989 s.12(2) when the Residence Order under s.8 was made.
A real example of that was decided by the Court of Appeal in 2008 in the case of Re A (A Child: Joint Residence/Parental Responsibility)  EWCA Civ 867
. The mother's former partner was not the biological parent of her child, but he brought up the child whilst they cohabited. The court made a joint residence order to ensure that the ex-partner would acquire Parental Responsibility and so prevent the mother from marginalising him in the future upbringing of the child.