Watch Da Birdie
I buy cakes for myself on my birthday it's not weird lots of people do it I bet
Jolyne's mother was actually a character introduced in Part 4---Shizuka Joestar. She grew up and Jotaro fell in love with her despite technically being his adopted aunt, so she was actually present during the entire plot of Stone Ocean but you couldn't see her because Achtung Baby made her invisible.