I really don't think there can be or should be anything to use as an excuse for breaking up a long built love. As a 5Th year medical student from all I've learnt till this very moment,the very reason why science brought the genotype thing to the knowledge of people which was a long time ago was :
1. Because there wasn't any technology then that could help manage sickle cell diseases . and
2. For people not be very careful on most decision they make so as not to bring to this world innocent children that will come to this world and suffer from all of those sickle cell pain from crises.
But then these are no longer excuses cos, among 4 children they may want to have as both AS persons, only one kid will be SS, 2 will be AS as the parents and One will be AA and with modern technologies now, there is a cure for sickle cell though has not been generally practice round the world but last year in one of the states in Nigeria, there was a successful treatment of a sickle cell kid who is now AA as a result of bone marrow transplant.
So therefore, i think dat love conqueres everything and if really they both really are in love with each other as they claim, their genotype shouldn't be a barrier. People who should be more concerned are those who are both SS or an SS and an AS.