Stem cells are undifferentiated cells that are capable of forming the different cell types that make up an adult individual. Thanks to their ability to differentiate, stem cells are of great interest in various medical fields. Their greater histocompatibility is also interesting, so that this cell type can often be used within families. 

The probability of finding a compatible donor outside the family is 0.001 % (1 in 100,000 people). For siblings, on the other hand, the probability of a match is 25 % (1 in 4).

This means that the stem cells of your child that you have stored after birth are very likely to be compatible with the siblings.