My younger sibling, who is 6, has been waking up in the middle of the night crying. My mother or father checks on him, but when they ask "what happened?" he is unresponsive. He doesn't say a word and keeps crying until he falls asleep again. He sometimes sleeps with my parents, but not so much and my parents are fed up with it. He is also very smart (he is in kindergarten but reading third grade material and he can add, subtract, and multiply).
I think it’s wonderful that you show concern for your little brother. I know sleeping issues can be stressful on the whole family! What your brother is experiencing is completely normal. Some children go through phases where they are prone to bad dreams, and a natural response after a nightmare might be to cry. Also, all of us go through different stages of wakefulness while asleep, and during deep sleep we may seem almost nonresponsive. It sounds like your brother might be in this state when your parents are trying to comfort him. He might not even remember the event in the morning. I would be more concerned if this is an occurrence every night and how much distress (if any) it’s causing your brother.
Lots of parents try to cope with restless nights by allowing a child to sleep with them, but there are strategies that may help little ones stay in their own beds. For example, bedtime routines should start in the child’s own bed. This allows parents to slowly move away as the child falls asleep. Remind your folks that periods of crying during the night are normal as your brother learns to self-soothe. Of course, if this problem persists, or if there are some stressful situations going on at home or in school, seek additional advice from a mental health professional.