My mother died when I was young, and for years it was just my father and me. When he told me he was getting married again, I smiled and said I was happy for him.
I wasn't. I felt replaced and irrationally angry that he could love someone after my mother. His wife turned out to be kind and never tried to become my mother. It took me years to appreciate her. I'm ashamed that during her first months in our family, she was trying so hard while I privately wished she would disappear.