I once asked a seven-year-old what it felt like when her mom married her stepfather. She said, “Well, it’s kind of like when a friend pushes you down on the playground and runs off and leaves you.” Ouch.
The problem here is that mom threw all of her time and energy into the new relationship and it came at the neglect of her child. If you are a single parent I suggest a good balance in dating. Spend time with your kids. Spend time with the person you are dating. If you are already married in a blended family, keep a fresh connection with each child. Ironically, this will make it easier for your kids to embrace their stepparent and stepsiblings because they are not competing with them for you.