Okay, so, I've been trying to figure out whether or not is possible for one family member - in this case young adult - to move out from under his parents roof and take some of the larger objects with him? For instance, there is a time machine and a miner his grandmother build, when she was alive. I would hate to leave those behind.

I've searched this forum and googled for the answer but without any result. I'm sorry if I managed to miss it somehow.

The only way I know of is to move using the 'move out' phone option (not by splitting up the family in Edit Town.
If you have the YA phone to move and, and make him the active family during the move out process, he will take everything that is in the shared family inventory. So if you put the items you want him to have in the family inventory, it goes with him. You'd have to take out anything in there you want the family to keep. The downside is the YA also takes the family funds.
If you use master controller, you can transfer money back to the family, however.

Thank you. I wasn't aware that the one moving out would have the family inventory items. Before, the parents have always died, because I wanted the young adult to keep the family house and have some ghosts, too. Now it's time for a change. This was a huge help. Thanks again.