I think that a family agreement like yours, which only has a seal, no personal signature, no personal fingerprint, and no certifier, should be invalid. If all three parties acknowledge the content of the agreement, then there is nothing wrong with it and the agreement is legal. If one party raises objections, the content of the agreement cannot be true. You can think about it. The state now controls the official seal engraving procedures. If there is no letter of introduction and the official seal is not engraved by the state's legal official seal engraving department, the official seal will be invalid and illegal. However, the engraving of personal seals should be said to be relatively chaotic. If this agreement is recognized as legal. The three parties, father and son, can go to the private stall to engrave other people's private seals, write an agreement casually, and then stamp each person's private seal as a legal agreement to satisfy their personal interests.

Wouldn’t that kind of law be a mess? What do you think? Good luck!