Hey if you want to take that up with Europian Royality, then by all means.
The problem with the spread of STDs, no matter if it is hetrosexual or homosexual, is the lack of personal responiblity in how a person is not careful about who they choose to be their partner and about how many partners they have had.
The have royalty on the moons of Jupiter already? Damn, I knew we should have put more money into the space program!
Just kidding, I know what you meant about the royalty.
The spread of STD's is a result of not having any societal shame or ridicule for sleeping around.
When virginity is seen as a stumbling block to social acceptance then it is no wonder that sexual promiscuity will follow with all its attendant problems.
Name one father and daughter 'relationship' (or mother son) in European royalty. The last sister/ brother marriage that I can think of is Kleopatra, but that was before Christ and in Egypt.