I don't know what your big brother said when he called you. What he said may be the reason for your nightmare. If you just want to know the meaning of this dream, this dream is only caused by your worry and anxiety, and your responsibility transfer is also reflected in this dream. Dreams are all in disguise. If you uncover this disguise, some evil thoughts in your heart will be revealed, which can only be seen by analyzing dreams.
The background of your dream happened when you were a child, which means that you have been sleeping for a long time. This dream shows your subconscious thoughts and memories. You dreamed that when you came home, you saw your big brother leave, but you didn't see the scene where your big brother hurt your parents, which means you imagined the scene of the injury (how do you know that your big brother gave your parents medicine? ), just the eldest brother left. Here, the dream expresses that the eldest brother ran away from home and left his parents behind for you, while the dream of giving medicine to his parents expresses that your eldest brother ran away from home, which is tantamount to murdering his parents and leaving them behind. This is the first half of the dream. The disguise of the dream is to hide the meaning behind the dream, which is usually shameful, so the dream has to be disguised. I can guess the hidden meaning of this layer is: you shirk the responsibility and obligation to take care of your parents to your eldest brother, and you think that your eldest brother has all the responsibility to take care of his parents. This meaning is covered up by the dream, which means that the departure of eldest brother in the dream is tantamount to murdering parents, and the death of parents is caused by the departure of eldest brother. And when you imagine that Big Brother wants to murder your parents, it is completely your subconscious to shift the responsibility to Big Brother. To show that you have nothing to do with the death caused by your parents' neglect, you will dream that your eldest brother killed your parents. Hehe, it sounds scary and incredible, but people's subconscious has the nature to find reasons for themselves. This is Freud's view. Human nature is exposed vividly behind the dream, and the idea that exists in your subconscious is also exposed, and this idea is the reason for this dream. Because people's dreams are designed by their own subconscious mind and have nothing to do with others, you can design your big brother in this way in your dreams, which also shows that you have some prejudice against him. In terms of taking care of parents, it may be caused by his poor performance, but in reality it is not easy to happen in dreams, so your worry is unnecessary.
I just explained why you dreamed of such a thing, and the second half of the dream had a similar meaning. If you still want to know, I can continue to analyze the dreams behind. At the same time, I hope these explanations can help you