In the early 70s, Filmation did really bizarre crossover TV special with the Groovie Goolies and a few specific Looney Tunes characters, including Petunia Pig, who actually played a relatively sizable role in the special.
It's occured to me that . . . I've never seen an actual Looney Tunes or Merrie Melodies cartoon that actually had Petunia Pig in it. At all. Whenever I've actually seen her, it's been in other things, such as comic books, merchandise, promotional material, and other such things.
And given that in said material, she's usually seen with Porky, one could conclude she's either a love interest or a female relative (like a sister) of his . . . but again, I've never actually seen her in cartoon form alongside Porky. In fact, almost all Porky Pig cartoons I've ever seen, he's usually paired alongside Daffy Duck as a comedy duo (where he's usually the straightman to Daffy's foil), or with Sylvester where he's apparently Sylvester's owner, and Sylvester acts more like a house cat than he does his usual crafty, coniving, Tweety-chasing schtick. Heck, I've ever seen odd cartoons here and there where Porky basically carries much of the cartoon himself without any other major Looney Tune characters.