I agree with the others who recommend you take the November siblings and then give it your all to make things work with that family. It is first come - first serve. It would be different if they were both wanting a November start and you had to choose but in this case - I think it's the November family who you should try to give a fair shot.
Then reassess what your situation looks like in April/May and see if you have any other spots open or what. That is a long time - someone else could still get pregnant and have a baby in that time so I would not plan things that specifically until I get into the spring of 2016.
Good luck