回复：回复：Wrong Idea

Yes. For different purpose.

If A and B are married and the cash in the join account does not have tax consequence.

If A and B are married and B wants to save something for father BB. Then A has to let this money go. That is when the will and marital agreement kicks in.

If B wants to pass BB some money and B is single, that may work well. Since B is married, then A has to give up his share.