An interesting new publication from the University of Oxford examines an area that perhaps rarely receives attention. The Impact of Fostering on Foster Carers’ Children argues that when foster children enter a new family, it is in fact the whole of the host family that fosters, and so the existing children of the foster parents also have an important role to play in this process. The research was carried out by The Rees Centre for Research in Fostering and Education, which has also released several other freely available reports.
For further reading on fostering, this previous post contains a number of suggestions (most of the links still work!), or you may want to look at the NFER's 2012 report: The Experiences of Fostering and Adoption Processes: the Views of Children and Young People.