You should talk to your friend before dating their siblings
Jacob feels attracted to his best friend's sister and thinks that she might also be interested in him.
Jacob wants to ask his friend's sister to go out on a date.
Jacob asks his friend if he is okay with Jacob asking his sister out on a date before he asks her out.
Jacob asks his friend's sister to go out without asking his friend, who is shocked when Jacob shows up at his house for the date.
Jacob's friend feels happy that Jacob confided in him first.
Jacob's friend is mad that he hadn't said anything to him first.