Is it ok to move my husbands sons out of their room to make room for the baby?

I agree with you for the most part, but it's still a sticky situation. Naturally you are excited about your new baby and you want to get things ready for her, especially fix up a nursery. You are going to need a lot of room with the baby, and if the boys are not there all the time, I think that's ok under the cirstances. I do think that you both need to sit down and talk to the boys and explain the situation, because it is so important that they understand that they are just as important as the new baby. At 12 and 13 I'm sure they'll understand. Also, you are correct in uming that they will begin to come to stay less and less as the next few years roll by, so all in all I think you should be able to use the bedroom for the baby. If the boys know that you are waiting for the three bedroom, then they know you're thinking of them too. Good luck with your baby !