Ahhh. This sounds so familiar.
My brother in law lived with his parents his whole life except for the 4 years while he went to university. As soon as he graduated, he was right back in his old bedroom. And he continued to live there.
In 2006, my in-laws decided that the three story house was too much for their advancing age and state of decrepiitude. They
first began going through their stuff and deciding what they would take to the assisted living center. They were moving from a 4 bedroom house to a one room apartment. Those decisions were not too painful and they moved their bedroom furniture, two favorite chairs and a desk, TV and computer into an assisted living center and told their son that he would need to find a place to live.
Leaving most of their worldly belongings in the house was not too painful. They could live where they had help and on the weekends their friends or family would take them back to the house so that they could go through their "stuff."
Throughout the process, in-laws kept on telling 46 year old son that he needed to get ready to move. He never went through any of his stuff.
Over many months, they would go back to the house and go through their things and decide that they could not bear to get rid of 80% of what they had. That 80% would go right back on to the shelves, back to the basement, etc. It was a long and painful process to get the house into shape to sell.
After 14 months, they put the house on the market. They continued to tell their son to get ready to move.
After 4 more months, the house sold and was scheduled to close in 30 days. BIL was FURIOUS that the house had been sold right out from under him!!! Truly! He complained about until both of his parents died.
Get rid of the kids stuff first.
elaine