He thinks he's doing a good job at babysitting but the kid is terrified, he wasn't trying to be scary. He was happy to at least try and bond with your siblings even if it was just him trying to make your family proud of him, he wanted to be accepted into your family and if that meant taking care of your sibling first then that's what he would start with. He loved you, he liked the kid even if the kid only screamed, to be expected from a toddler.. but he wanted to make your family accept him