In the Season 2 episode “Something Smells,” SpongeBob’s best friend comes to the realization that he stinks. Not having a nose to smell himself, this comes as quite the shock to the sea star, who begins frantically spiraling as the gravity of his situation dawns on him. As he babbles about the consequences of stinking, he exclaims, “Oh gosh, if my sister finds out — oh, wait. I don’t have a sister.” While it seemed like Patrick was just letting his paranoia get the better of him, this little tidbit of familial information didn’t hold up as more episodes of the show came out.
By the time the Season 7 episode “Sam Star” premiered, it became apparent that Patrick isn’t a reliable genealogist. The episode features Patrick’s older sister, who comes to visit him and his friends in Bikini Bottom. This might be a consistency error in the show, but then again, if Patrick forgot what his parents looked like, it’s also totally possible he just forgot he had a sibling or two.
“The Patrick Star Show” further compounds the confusion, as Patrick makes a television show with his adoptive younger sister Squidina, who had never been mentioned previously, though she did appear in a few episodes as a side character. In the end, it’s hard to say whether Patrick doesn’t know his family or if he’s been disowned by his siblings.