Josh Wolowitz is Howard Wolowitz's younger half-brother. In "The Fortification Implementation", Howard meets Josh, his father's son from his father's second family, for the first time. Josh is an oceanography student from San Diego who learned about Howard after his mother's lawyers contacted him.
Josh first appears in "The Fortification Implementation" at Howard's late mother's house which he and Bernadette had moved into. He tells Howard how a lawyer contacted his father, Sam Wolowitz, about the title on that house. Since Sam was Howard's father, that makes the young man Howard's younger half-brother. Howard calls and tells Bernadette that weird things were happening.
Howard runs off to get more coffee leaving Josh with Bernadette and Raj. He is an oceanography student in San Diego; while Bernadette comments that she loves "Finding Nemo". Raj challenges him as to who he really is though who would still claim to be a Wolowitz? Does he want money, a kidney or for Howard to replace his father as Ringo in a Beatles' cover band as Bernadette decides to send him after Howard. Raj tells Josh that he wanted to hear about Josh's studies since it sounded cool.
Howard is upset and uncomfortable that Josh had showed up, as that meant his father had gone onto have another family after he left him and his mother alone. Howard wants to tell Josh to leave before Josh looks at Howard's old astronaut portrait as he excitedly exclaims that he can't believe that his brother was actually an astronaut, stating that it was amazing and asks what space was like. Raj tries to tell Josh that it's time for him to hit the road, but a flattered Howard cuts him off saying "Whoa, hey, hey. The young man asked a good question." as Howard starts to explain about the greatest adventure of his life to his now-known brother.Howard is entertaining Josh with magic which he finds pretty cool until he figures he has to go. Howard hopes to see him again as Josh states he does as well as he has always dreamed to have a brother to play catch while Bernadette tells him that he'll have to keep dreaming. Howard mentions throwing a pitch which impresses Josh, but Bernadette states Howard used a robot that he made to do it, and Josh thinks she means sex which Howard denies, but Raj confirms.
At the door, Josh asks his brother about the robot which Howard tells Josh was actually just a mechanical hand. Josh thinks that that is all he needs and Howard hugs him telling Josh that he is definitely his brother.
Josh does not make another appearance on TBBT.
At first, the meeting Josh had with his older half-brother was awkward but it got better as Josh thought it was amazing to see that he has a brother who is an astronaut.
It is shown he has a similar warped manner that Howard had before he met Bernadette. He understands about the robot arm that Howard used for self-gratification which causes Howard to hug him in acceptance, knowing that he is really his brother.