what to tell your kids

single mom, those of you have kids. At what age is appropriate to tell your child about parents are divourceed? What do you tell them? Is it the child asked? My ex husb has left me and my child almost 2 yr. My dau is 3 years plus. He hasnt been coming to see her. I am concern how to break the news where she start to ask where is the father. My ex hus has left us bcoz he wants his freedom, doesnt want any responsibility, affair and staying with mistress.