[Advice] How do you tell your toddler another baby is on the way?

Hello! Asking for my sister. She has a 2.5 year old girl and is 4 months pregnant. She's wondering if others who've gone through this had good ways of introducing the concept of a brother or sister? How long did parents wait to tell them? We're there books they used to introduce these ideas? How involved or not involved did you let your toddler be in the next baby? Any advice, stories, book recs are welcome! via /r/Parenting http://ift.tt/2cgfb3n