Hi! May I ask where is stated that Sirius was a player while he was a teen? I can't seem to remember if it was in the books, but every story, one shot, imagine etc. mentions it. Maybe I should go reread the books again? Thank you anyways!
I answered a similar question a while back: (x). The gist of my response was that I found these three quotes:
- “[Sirius] always got the women.” (From Remus Lupin’s Pottermore profile)
- “[Sirius] was very good-looking; his dark hair fell into his eyes with a sort of casual elegance neither James’s nor Harry’s could ever have achieved, and a girl sitting behind him was eyeing him hopefully, though he didn’t seem to have noticed.” (From OotP, Chapter 28)
- “Sirius was too busy being a big rebel to get married.” (A JK quote from the Edinburgh Book Festival, 2004)
And those quotes are really the only canonical/semi-canonical quotes that I could find linking Sirius and romance. None of them directly state that Sirius was a player in canon, but you’re right that it’s a very common characterisation in fan-created works. :)