Ask A Korean! Wiki
Ah, the genetics of red hair. Skin and hair colour come from the pigment melanin. There are two forms of melanin, eumelanin, which is black or brown, and pheomelanin, which is red. Crimson hair comes from having low levels of eumelanin and high levels of pheomelanin. Most classic, full-on gingers in virgin straight brazilian hair fact cannot make eumelanin at all because they have two mutant copies of a gene called MC1R, which causes eumelanin production. (Remember, you have got two copies of nearly every gene, so both copies of a gene should be dysfunctional with the intention to get the mutant phenotype.)
So, let’s assume that the gf has two mutant copies of MC1R. Which means the offspring are going to get not less than one mutant copy of MC1R. If the bf had been full Korean, he would positively have 2 normal copies of MC1R, and the offspring would have one normal copy and one mutant copy: dark hair, probably closer to brown than black, but positively not red. Nonetheless, the bf is half Korean and half Irish Canadian. If there may be crimson hair in his dad’s family (or even when there isn’t), the copy of MC1R from the dad could be mutant. If so, he’s acquired a 50% chance of a dark-haired youngster and 50% chance of a ginger.