is there a way to do more withe the brother at work ?
i always get this line
If only there is something that can help him lose his inhibition.
You should check the memories (gallery) after the game ends, it has the list of all the things you can see & do.
As for the things to do with him at the restaurant:
Fast food quickie: you need to have the first blowjob unlocked and meet him before 2 AM (if he works night shift) or 12PM (if he works day shift) and suggest any lewd activities to him. He'll tell you to meet him at the aforementioned times to give him blowjob
Fast food fuck: you need to have the first fuck unlock and him to be drunk (drink beers with him 2 times) before going to work. Doing the same thing as the quickie and you should get the scene.