No. Joint accounts held by you and Dad will belong to you when he dies. They will not be subject to his will. If you decide that it was really his intention that you share these equally with your siblings, you probably can arrange to do that, promptly after his death. Be sure to consult a lawyer. It may be easier to give them gifts, especially if this can be accomplished fairly quickly with gifts of less than $14,000 per year per recipient ($28,000 per year if you are married and wife cooperates). You will not be taxed on giving a gift and will not be required to file a gift tax return, so long as you do not give any one person more than $14,000 in any calendar year. Even then, excess gifts will merely reduce your lifetime exemption, presently presumably at $5.25 million, going up in January.
Answered on Nov 19th, 2013 at 4:37 PM