Welcome and thanks for your to HCM.
It appears from your query that you are quite concerned about your friend and his would be wife as well as for the future kids. Now answering your queries one by one:
1.For the couple it depends upon the status of their history of unsafe contacts or if have any sexually transmitted diseases then both can be infected. For the girl you said she had unsafe contact so it is now the girl's will to go for any tests regarding the same.
2. For the future kids also it is quite important for the lady to not have any sexually transmitted diseases.
3. for the last part of query, each individual is totally unique in itself and even twins grown in the same womb have different nature and hobbies, so it is totally impractical to think about any kind of characteristics and especially sexual hobbies can be inherited from the parents to kids.
Hope this information will help you.
Dr Sanjay K Kanodia
MD (Dermatology & STD