Is it wrong for kids to be upset or express dissatisfaction if their parents are having another child

I’m just wondering. My mom is pregnant again. I’m 15 and my sister is 10. We barely have enough money to live now. Just a few months ago we finally started being okay financially. My parents had me when they were 15 themselves so that kind of always made it difficult for us to have enough money for things. Yesterday my mom told us that she is pregnant and I’m not happy about it. I’m scared and annoyed. This will be their third unplanned pregnancy now. It’s just frustrating to me because my parents stress to me how I can prevent getting pregnant but they seem to not take their own advice. My dad is like my best friend and now he has to get yet another job so I’ll see him even less than I already do. I don’t want to be annoying and rude to my parents but I’m really bothered by this. I told my grandparents that I’m unhappy about it and they scolded me for that. But I think I’m justified in being annoyed