Under the Civil Code of the Philippines, trespass occurs when someone unlawfully enters or occupies another's property. In your case, if someone changed the boundaries of your land without permission, this may constitute trespass.
In summary, the father may not legally sell the entire property without the children's consent if the property is part of the estate of the deceased mother. Any sale done without the agreement of all heirs can be contested in court and possibly declared void.
If a person other than the owner attempts to sell the property, the transaction is considered illegal. This type of sale falls under fraudulent transactions and can be nullified under Philippine law. Even if the buyer was unaware that the seller was not the legitimate owner, the sale would still be void.
In general, once a seller has signed closing papers and the transaction has officially closed, they cannot back out of the sale without facing potential legal consequences. However, there are a few exceptions and considerations:
The sale, mortgage, or disposal of conjugal properties in the Philippines cannot be done unilaterally. Both spouses must give their consent before any such transactions can be validly executed.
Methods of Property Transfer This can be done through either a sale or a donation. Sale: The parent may opt to sell the property to the child, either at market value or below. A notarized Deed of Absolute Sale will be required, along with other documents, such as the Transfer Certificate of Title and tax declarations.