Reading this and your previous posts, you have not fully outlined your financial situation. Especially do you have a mortgage on your home.
On the limited info you have given, my advice is that if you sell the investment property and have a shortfall of €100k. You should NOT take money from family to settle with the bank. And don't raise this as a possibility with the bank or they ail try to force you to give them that money.
You will then have an unsecured loan, which you will be unable to repay. Will you be unable to repay, you haven't given much info.
The bank will then take you to court to try to force you to pay.
The court then has 3 options
1. Order you to pay €x amount each month, based on what you can afford. This is called an instalment order. Generally courts seem to be sympathetic to people in this situation and make affordable orders
2. Register a judgement mortgage against your home. This means that were you to sell your home within 12 years you would have to pay UB. But a judgement mortgage does not force you to sell.
3. Order repossession of your home for UB to sell. Old Nick has posted that this could not happen. I am not clear why he says this. I agree that a judge would be slow to put a family out of their home to satisfy a debt that is not secured on it, but I would like to hear why Old Nick rules this out completely.
There are two further pieces of info which may change this completely.
1. Is the loan on the investment property secured against your home.
2. Have you a mortgage on your home, and if so who is it with.