Every woman will die in five seconds.
Mother: Dies.
Sister: Dies.
Girlfriend: Lives.
You: 🤬
Hey, genius! The joke is that the person telling the joke is mad that his mother and sister die, but his girlfriend lives. It's funny because it implies he doesn't like his girlfriend as much as his family. Also, the joke is made even funnier because, like you, it's super misogynistic!