Hi J. :-)
It seems you have multiple transitions going on at once which may be too much for your 17 month old to adapt to. You mention that he has been sleeping with you and your husband for the past 8-9 months. So I might suggest that in order to help this young one with the transition to a NEW home which is a huge move when little ones need to know that things are safe and feel familiar... that you continue to allow him to sleep with you and your husband as you have been doing.
After a while, you can begin the transition to the older brother's room which is the one they will share. Maybe one night a week put him in there, and then slowly increase the days of separation from your bed into his own bed in his brother's room. You may also put him in the new bed in brother's room and lay down with him until he falls asleep and then kiss him good night and leave.
ALL of this with the suggestion additionally that you TALK with your 17 month old and explain about the new house and how soon he is going to be having his own bed and sleeping with his big brother! Let him adapt to the changes and keep it light and simple but fun!
hugs,
A. R.N., Energy Medicine Practitioner