Funny that you mentioned it..reminded me of a sci-fi "opera" called "Hydrogen sonata" by Iain M Banks.
It take place many eons from now and anyone can have any body they want and you can change the body too (the explanation would take too long to post here).
Anyway...One of the characters there had either a dozen or 50 penises (it's biological engineering, of course) and, indeed, he had to have multiple hearts with most of them activating only upon a need to pump blood in those organs upon erection, of course.

Somehow, it felt/read kind of gross, but I am sure that imaginary fella had a lot of fun, probably  .