Running a business with your sister is tough, unless you two have founded a Barbie salon, and it's your job to cut her hair. For funny t-shirts from a brother/sister pair, check out Metasaurus
From an ex-graffiti artist (nicknamed "Meta") and his bike-loving older sis, 'saurus is a San Clemente-based tee op that churns out funny threads in limited runs because their creative minds aren't looking to mass produce, and are "never short of graphic content", so hopefully they've figured out how to delete the history on the family desktop. True to their name, they've got dino-related awesomeness like "Shredder Saurus" with a fully padded T-Rex tricking off a lightning bolt (an old-school nod to Santa Cruz's Jim Phillips), a stegosaurus skull & crossbones emblazoned with "Save a Dino Ride a Bike", and "X-Ray Spex" with a lizard donning shades and looking all pleased, probs 'cause he can see right through all the chicks' tricera-tops. They've also got playfully morbid numbers like "Modern Car-nivores" with a fanged car chomping down on some bicyclists, the not-so-ominous "Death Rides a Pale Horse" with a reaper and his 10-speed, and a pair of jigging skeletons (inspired by a late friend's infectious positivity) called "Dead Can Dance", a fact Bernie clearly supports, assuming he's on a see-saw
Cause it's not all about death and dinos, they've also got the "radio poster style" "World Takeover Schemes" featuring a War of the Worlds-style monster named "Hugemongous" -- also what you deemed Barbie's coif before giving her a tasteful buzz.