The galactosemia is a condition, in which the affected person is not able to metabolize the galactose sugar. This is a genetic disorder, inherited as an autosomal recessive trait. The homozygous dominant and the heterozygous individual do not show this condition. Only the individuals having homozygous recessive trait will show this condition.
Lets say allele G codes for galactosemia, and G codes for the dominant allele, and g code for recessive allele.
The attached image shows the possible pedigree of the Justin’s family.