Saviour siblings are children who with respect to their suitability as a blood or tissue donor are able to help out an older sibling with their treatment. As the parents are not suitable as donors due to wanting HLA compatibility, the embryo with the highest genetic congruence with the ill child gets implanted after an in vitro fertilisation via PGD. After giving birth the stem cells of the cord blood or the bone marrow of the new born shall help the ill sibling.

In March 2003 the first saviour sibling was born. At that time it was supposed to rescue the life of the four-year-old ill brother, who was urgently in need of blood stem cells. The parents received the PGD in the USA at that time to evade legal problems in their home country. Meanwhile Great Britain relaxed the regulations in this respect. In Sweden the application of PGD in order to produce saviour siblings is also permitted. In Spain in October 2008 the first baby generated this way was born. The brother of this child suffers from a genetic blood disease. As early as seven weeks after the ill child received stem cells from the cord blood of the newborn, the first successful results could be observed. The doctors report that the seven-year-old boy has almost overcome his illness.

The generation of so-called saviour siblings has to face loud criticism and is seen from many sides as the first step towards so-called 'Designer Babies'.