Check with your county laws.

When we were fostering it was strongly encouraged to not foster/adopt out of birth order so we only fostered kids that were younger than our kids at home. Our first foster placement was a 5 year old boy and 2 year old girl. Our other kids were 6 and 10. We eventually ended up adopting and it turned out great. Our second placement was of an infant. We were able to adopt her as well. We knew we wanted to adopt so we looked at low risk situations. In the case of the bio sibling set, their birth mother had left the country. They were living with their biological grandmother and she couldn't take care of them any longer due to health issues. They were a foster to adopt situation. In the case of the infant she was born to a woman who was serving a lengthy prison sentence and had already lost custody of her older two kids. That family didn't want another child so we were contacted since we were open to all of the health needs. Our kids are 17, 13, 12, 9, and 6 now. I wouldn't change anything we did.