Finn and Princess Bubblegum are the parents of Stormo. Finn and Ice King are the parents of NEPTR. Finn and Magi are the parents of Little Dude.
Jake and Lady Rainicorn are the parents of the Corndogs. Jake and Lady Rainicorn are the uncle and aunt of Finn's children.
Princess Bubblegum is the parent of the Lemongrabs. Princess Bubblegm and Finn are the parents of Stormo. Princess Bubblegum is the grandmother of the Lemon Children.
The Lemongrabs are the parents of the Lemon Children.
This is really confusing so a more complex chart would be appreciated.