Date: December 03, 2017 12:17PM
In a North American context, it would depend a very great deal on what "kind" (specifically) of Buddhism your BIL identifies with because there is a huge spectrum of Buddhist belief, of Buddhist observance (or lack of observance), and of Buddhist communities or groups.
I was raised (primarily) Hindu/Vedanta, and since the Buddha was born Hindu and then, later, became the first Buddhist, and since there are many kinds of Buddhists and Buddhist temples in the area where I live, Buddhism has always been one stream among many in my own, local, greater culture. Buddhism has always been a peripheral part of my life (it is literally "around" me in my life), but I actually "know" very little about it (for one thing: despite "knowing" for virtually all of my life that there are two major, important, divisions in Buddhism, and despite having these carefully explained to me on different occasions, I still cannot describe either one of them!).
During the time I was working at Los Angeles City Hall (my first job out of high school), I went to several Buddhist services at two different temples in Little Tokyo (which is adjacent to City Hall)...
...and, although we do have a major Buddhist temple in the San Fernando Valley, and although I used to be a regular and appreciative customer of a really wonderful Buddhist vegetarian restaurant fairly near to where I live (they have a bookcase nestled against one wall, with Buddhist publications in it which can be read while you eat your meal, if you are so inclined), none of this ever "took" with me.
I am just not on the same wavelength as Buddhist philosophy and thought.
Because the differences between the different Buddhist groups are so pronounced (at least they are from my, non-Buddhist, perspective!), I think you would probably have to know more about your BIL's specific "kind" of Buddhism before you could begin to understand where your BIL is coming from. Potentially, it could be any of a wide spectrum of possibilities (starting with: which of those two main Buddhist traditions does your BIL subscribe to?).
I strongly suggest that you go over to You Tube and search for "Buddhism," where you will find a great number of videos, some of which are likely to answer your questions (and some of which are, like most of the You Tube religious/philosophical subjects, off-the-wall...so be cautious in what you decide to accept as fact, because just because it is on You Tube doesn't mean that whatever-it-is is factual).