My sister and I both studying at the same uni about to graduate (twins ;22 yo) lived together for a year at my dads house who works long distance. A year later my dad tells us that our adopted brother that we don't have much of a relationship with ,will be staying with us for safety reasons because of an assault court case. Mind you he is 30 yo and unemployed; he just graduated with a random degree however he has no intentions of working at all. After being around for him 1yr albeit on and off I have recognized that he is a hobosexual. The area he lives in(his mom's house) is low income so there are always power+water cuts. Whenever there are power,water cuts he comes to the house. Now he has began a new thing where he comes to the house on my dads pay day &leaves on his mom's pay day. I know my paragraph is long but context is important!!! Anyways, my dad only gives a certain amount for household essentials every month so it would make sense to be mindful of consumption and to be as sparing as possible & my sister and I communicated that to the adopted brother. Well,this adopted brother interpreted that as my sister and I saying don't eat anything and that we were just being stingy /mean I guess.Him and his mom started subtly& passively aggressively hinting towards this & implying that my sister and I are "excluding" him from household resources. Mind you this is a 30 yo grown adult man who I don't even know like that fr😭😭. Anyways one day he comes to the house ,as usual,it's when there is a water shortage at his mom's and he then asks me what do U eat for lunch. I then said U can eat whatever you want and proceeded to list the lunch food we have. The following day he started cooking full on meals for himself in the middle of the night when he thought we were sleeping. At first I thought I should say something however when this first happened when he moved in, I asked my dad to talk to his adopted son about consuming household resources sustainably because maybe he isn't used to that since he is an only child; however my pleas fell on deaf ears so when he started being wasteful I decided to just not say anything because it's not fair that I have to be playing the bad guy & monitoring a 30yo meanwhile my dad just gets to be the nice,chill guy because that is what was happening.So here we are now in a situation where it's only halfway through the month and most of the food is done, electricity is also basically done and my dad will be coming home this weekend to a half empty fridge and little to no electricity. For those who might say I just don't like the adopted stepbrother I don't know him, I only met him once 15 yrs ago so I have no reason to not like him. Tbh when I heard that he was 30 and unemployed I anticipated everything and I was right. So I just want to know AITAH for not correcting my 30 yo adopted brother's wasteful consumption?