How should I respond to this person?

Well, I'd say that after he's sniffed out the "meekness", and he's been in the business of intimidation because he can get away with it. The situation has nothing to do with age and I think you have essed the problem correctly in the word "respect". So you want that? Then, pively demand it from him. Don't act meek around him; look him straight in the eye and perhaps get into his personal space and say "how you doin', Joe?" and give a wicked smile. You don't have to be mean, but you can mirror his actions and really freak him out and demand respect. Maybe you should somehow let your sis in on the plan since she may feel a need to defend him. Do some research on "mirroring". I think you're intelligent enough to work this out with a little psychological probing. One other point: he may have a crush on YOU! Don't count it out. Godloveya, honey. You're on the right track!!