The Wild by Esther Freud
Published by Penguin

Nine year old Tess and her brother Jake live with their attractive mother Francine, in shared accommodation with teacher William and his daughters.   Tess is very drawn to William, seeing him as a perfect father figure.   It is the 1970s in England and the children are all adapting to new adult relationships.   For Tess and Jake things are especially difficult, and through them we experience the pain of growing up when adults are in control.   New pets and eventually new babies arrive.   Visits to other parents punctuate the rustic lifestyle.   However Jake's lingering resentment leads to near tragedy and once more his family must move on.