Effect on Biological Children

i have been a foster parent for 4 years. initially, i did not have other children, recently i have adopted my almost 3 y/o. i am fostering his 1/2 younger sib. she has been with us for 11 months or so and will be returning to her bparents. this is the first foster child in my home since my son. i am anxious to see how he does and if any one else on the forum has any suggestions on how to make the transition easier on him. thanks for the thread, i can't wait to see what others have to say.