Yes and no. One little boy I know will repeatedly wish his little sister would go away and that he hates her. He doesn’t really, although that may be the way he feels in the moment. Most brothers and sisters feel this way at some point, and time apart makes it easier. This particular little boy is on the high functioning end of the spectrum, obviously, because he is able to vocalize his annoyance and frustration about a younger sibling. Although he should be encouraged to say how he feels, it is also a teachable moment for his parents to ask him how he would feel if he really didn’t have his little sister around.
Since he also vocalizes when he misses his sister and that he loves her, and that he does show her kindness and affection when they feel like playing together, his parents can help him reflect on the positives of having a sibling and the negatives of not having a sibling to play with during the good and fun times. Often this little boy begins to cry and is very penitent about his words because he does remember that it is fun to have his little sister around once in a while.
The same holds true for ASD teens and preteens who tell their parents that they hate them or wish they were dead. It’s how they feel right then and there, but if a parent responds in a very loving manner, e.g., “I know you hate me and that’s okay because I still love you; you are my kid and I always will love you”, then the preteen or teen realizes that they haven’t hit a nerve with mom or dad and what they said wasn’t very nice. They calm down and then return to apologize, knowing full well that their parents really do love them and are only trying to protect them or help them.