The end of the article has several references to sources that can be followed and the references cited themselves contain links to supporting material. IMHO the prostitution/brothel claim against Frederick is a bit weak, but the draft dodging and other bits were all widely circulated over the past four years and extensively researched.
The refernces are found at the bottom of the article; one to wikipedia (so you can follow more references), and another to a book about the Trump family.
https://listverse.com/2017/01/11/10-terrible-things-done-by-...
https://www.thedailybeast.com/the-myth-of-joe-kennedys-bootl...