AITA for keeping the whole tip for myself?

I work as a janitor at a college. I’m a student, so it’s student employee position. A lot of people work in the department and there are usually 25-30 people in our area. People usually bring in $5 or $10 or so occasionally to give us as a group. I’m usually the person they give the money to because they see me sweeping and I always say thank you and promise to pass it along. I usually spend the money on food. <br><br>My brother was in a bad accident last week. He had brain injuries and the doctors said it was touch and go. My parents had to fly out to where the accident happened to see him and they were worried about money. So I was stressed out about that. <br><br>Yesterday someone gave me $100 and told me to split it with my coworkers. I was like fuck it and kept the whole thing. That money can help pay for a plane ticket or hotel for my parents if they need it, and I can always replace it by giving them back $100 worth of food. But if they don’t need the money I can use it to pay my tuition.<br><br>My parents always said not to rely on tips and that tips are for extras, not for paying your bills. So I don’t even get tips at work but my brother being hurt makes that different. <br><br>My girlfriend found out I kept the $100 and thought I should split it. She said that my coworkers count on tips and that if they find out they will think I’m a shitty person.<br><br>AITA?