I like coffee a lot, but it does not have an effect on me. It actually puts me to sleep. My brother is the same so it may be genetic (but I did not do research

I like coffee a lot, but it does not have an effect on me. It actually puts me to sleep. My brother is the same so it may be genetic (but I did not do research on that). I often drink coffee before going to bed, even strong ones. This always makes my parents and wife worried, despite the years. I like the taste very much but if there is no available I am just sad and drink some water. For some time I was missing coffee at home and it took me some time to go shopping some, because lazyness and procrastination. There are times I drink 6 or 8 espressos a day (without any special reaction), then days without coffee, then a few a day, etc. No withdrawal effects.