I believe you're right about the wait time for children around 3-5, when it is just one child. The wait for a 0-2 year old is about 30+ months right now as well, through ICBF. If you adopt a baby through a private casa, the wait time may or may not be less...seems like some have been around a year or year and a half, but I believe this is the wait time that people are more unsure of how it will change with the implementation of some procedures.
I know exactly how you feel regarding siblings...same with us. I do think that someday this might be something for us, but most likely not with our first.
