Dog aggression/sisters new baby

My dog is 5 years old (I just personally started taking care of him a couple years ago) he was never trained as a puppy and growls, barks, goes after strangers in the house. My sister (doesn’t live with me but visits atleast once a week) is due to have a baby later this year and I was wondering if I should continue to be as nervous as I am about my dog with the baby, or if he’ll do better than I expect. He’s not aggressive at all towards my sister, he actually really loves her, he did have a problem with her husband at first but has grown to like him also. I’ve also started to play baby noises from a stroller and try to act more as if there’s a baby in the house, just to try and get my dog used to it. Any advice or insight into how my dog will (hopefully) react, I know there’s no guarantees

Hi! Thank you for the topic, as such I can't help you with an answer, since I myself now need such information

This is a typical animal behavior caused by fear. Sometimes dogs tolerate the presence of a small family member around until he starts to bug. In this case, aggression is a reaction to an unpleasant stimulus. The second reason for the manifestation of aggression is a rivalry. If the child is perceived as a rival and infringes on the owners' attention, then the dog may make a menacing growl. First, with the help of online service dog registration, you must make sure that your dog is completely healthy, has all vaccinations, and does not have mental disorders. Then you can start training your pet. First, teach the dog simple commands - "come", "place", "stop". Your task is to achieve impeccable obedience. So in the future, you will be able to walk with the dog and the child.