Impact on other children in family

Hi there,

Im just wondering what you feel is the impact that adoption can have on other children within a family (for want of a better term 'biological'). When I grew up some of my extended family often had children in foster care coming in and out of their family and there seemed to be a lot of friction between their kids and the kids they took care of. Now fostering children isnt exactly the same thing but what do you think is the best way to prevent any emotional problems for either party? how can you maintain harmony?