My brothers have a habit of saying the n word while making jokes and stuff. sometimes they make a joke that is funny but they say the n word in it and I laugh only cause the joke is funny not cause I’m pleased with them saying the n word. Am I sinful for this?

Laughing at what is funny is not a sin, but the word itself is belittling of people and that is forbidden, so do not let your laughing be the thing that encourages them. Remind them of Allah and tell them you do not accept it, and if you advise and it changes nothing then you should move away from them when they start joking like this or start looking for pious friends that increase your iman.