This covers only one scenario. What about other possibilities where mother and father of a kid died who has passed breast feeding age ?
Bukhari mentions many ahadees in which even grown up kids touching puberty were breast fed by women even the days of Rasool Allah(SAW) but those ahadees go against teachings of Islam.
Good question.
Good questions. Adoption is not against religion , but what to do in these kinds of situations needs some research. When there is a will there is a way . If Islam does not disallow adoption , but there is a concept of mehram and na mehram then these questions need to be answered in the light of shariat a Mohammadi(SAW). If I get time I will do some research to answer all these good questions. Intezar farma-e-a