There is a thief in our home

There is something wrong in our home. There is an untrustworthy person.
This afternoon, when I came home from school, there was a piece of inconvenient news. The news was someone had stolen some money from the shop. The stolen money was estimated around 300 thousand Rupiah. And it has something to do with me. Here is the story. As usual, everyday I keep the phone shop from afternoon till 9 pm at night. After going home from school, I take care of myself and be ready at the shop to help my sister in-law. My sister in-law usually goes with her friends at night and she often asks me to replace her position. Last night, as usually, I kept the shop till 9 pm and then I closed the shop. Before closing the shop, I counted the money which was around 300 thousand Rupiah or more then I locked the drawer and put the key in the room in which my sister sleeps. I usually put the key there since my sister in-law does not live in the same home. She lives in her own home. This morning, when I came home from school, she asked me a question, “did you bring along the money with you?” As I usually do. I said “no, I didn’t” I left all the money in the drawer. Then we understand that the money was stolen and the thief might be someone inside the home. We don’t know yet who stole it. This is the second incident in this month. First, my real sister’s money was stolen few weeks ago. The amount was 300 Malaysian Ringgit. The incident happened at daylight too. Till now, we have the accused already but we haven’t got the proofs yet. To some extent, I felt a bit uneasy with my sister in-law because she had lost some of her money. I feel that there is a burden in me to find the thief and prove that someone has to be responsible for his action. The suspected man is her brother. He has a bad record in the history of stealing his own family money. I don’t know what to say about him. I am blind and I don’t fit well with him. A reason why I don’t get along with him is in my observation he is a drug user. He has had a therapy in Bogor but I think he has not changed. He still likes going to pub, discotheque and such kinds of places, in which he is close to drug. I am pity on him to a certain extent and to his parents. He is almost 40 years old. I am so sorry for the stolen money and for the story.