Children born to parents with blood type O and B are usually of blood type B or O. The human blood type is usually categorized as A, B, O and AB. Human blood types are usually categorized into four types: A, B, O and AB. The A and B genes in human chromosomes are dominant to the i gene, and the genotype of blood type O is usually ii. The genotype of blood type B is usually Bi or BB. The genotype of blood type B is usually Bi or BB. According to the Mendelian law of inheritance, it is possible to give birth to the offspring of Bi and ii, that is to say, it is possible to give birth to a child with blood type B or O, but it will not give birth to the offspring of blood type A or AB. Human blood type generally remains the same throughout life. Blood type is inherited through the chromosomes in the cells, and the genetic locus of the ABO blood type system is on the 9th pair of chromosomes, which can be analyzed for determining paternity or used for other treatments.