Salam! Aah tau lah, anak 3 tahun memang supposed to be calmer but honestly if ada adik coming, emotions dia lagi gila-gila lor, it's a big deal untuk dia! My mum friends and I agree, anticipation of a sibling often triggers tantrums even at that age sebab dia confused and excited mixed together. Lagi-lagi if dia dengar conversation pasal baby coming, the anxiety boleh jadi trigger jugak. As long as the tantrums aren't extreme violent behavior, it's pretty normal during this transition, just reassure him lots and keep routines consistent yeah.