The blood groups of children can be determined precisely based on the parents’ alleles. There are some interesting possibilities and also limitations.

Two parents with blood group 0 (00 and 00) can only have children with blood group 0.

When both parents have blood group AB (AB and AB), their children can only have blood groups A, B, or AB, but never 0.

Inheritance follows fixed rules and can be clearly illustrated with the Punnett squares.