LOL! My brother did the same thing but I rarely gave him a loan. That left me with even less to get through the week.
Our allowances were deliberately fairly small. That was to teach us to save if we wanted something that cost more than we got each week.
So he either backed off on his spending for a week here and there or did without . :-)
Well, it was very rare that I did and then it was the devil to get him to pay me back. I would usually have to end up being the tattle-tale to get the payback before he got his allowance. He thought I was the meanest big sister. LOL!
Ours was small too. I was a saver. I even bought some of my clothes when I was a teenager. I didn’t have a job, but I’d save my allowance, put something on lay-away and then had the satisfaction o self-reliance when I finally got to wear my new things. The ladies at the stores were very patient then. :)