Siblings sensitivity to kids with austism spectrum disorder (ASD)

Hello

My youngest (7) son has ASD. He is generally nice and playful and kind. But sometimes he does things that annoy his older brother and sister. They are 15 and 17, so naturally stressed with their study/class. Now they find very little time to engage with their little brother and he feels sad they don't play with him. Sometimes when my son does silly things i feel my older kids react to him harshly and get annoyed with him. I understand that my son does not act his age as he also has global development delay, so he acts more like a 3/4 year old kids, gets upset easily. I was wondering how can i help his older siblings to be more sensitive and understanding towards him. Is there any course /training that i can avail so they understand their little brother is different. I have heard that some siblings get training on how to deal with their special needs siblings.