IMHO I think Anthony heard his mother say she got an abortion. He was standing just outside the room where Kay and Micheal were yelling at each other so he had to have heard her. As young as he was at the time I think maybe he understood what that meant as her follow up to that was to yell, "It was a son and I had it killed..." Poor kid with a cold distant father then to find out his mother killed his little brother before he was born.

No wonder that boy didn't want to kiss her!