Adopting Siblings

My hubby and I are new here and have a couple of questions that we are hoping someone can answer. First a little background. We have been through all the foster and adoption classes and have been approved. We do not yet have our license but it don't seem to be to much longer. We have had all of our visits except one. This is the visit that is holding up our license we believe. We are wanting to adopt 2 sibling girls. But I am starting to change my mind. I am thinking now about a boy and a girl. The problem is right now we only have one extra bedroom. But we do have another room that we can make into a room when needed. Its just going to take some time to get a wall put up and all that good stuff. So my question is what is the oldest that you can keep siblings in the same room that are boy and girl? My last question is, when you get an approved home study are you able to start inquiring about children or do you have to wait on the license? Thanks in advance for any help and advice.