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It does appear that the surviving spouse and/or children have to sign waivers to accomplish your goal. Here is the relevant law:
§ 711.039. Rights of Interment in Plot
(a) A plot in which the exclusive right of sepulture is conveyed is presumed to be the separate property of the person named as grantee in the certificate of ownership or other instrument of conveyance.
(b) The spouse of a person to whom the exclusive right of sepulture in a plot is conveyed has a vested right of interment of the spouse's remains in the plot while the spouse is married to the plot owner or if the spouse is married to the plot owner at the time of the owner's death.
(c) An attempted conveyance or other action without the joinder or written, attached consent of the spouse of the plot owner does not divest the spouse of the vested right of interment.
(d) The vested right of interment is terminated:
(1) on the final decree of divorce between the plot owner and the owner's former spouse unless the decree provides otherwise; or
(2) when the remains of the person having the vested right are interred elsewhere.
(e) Unless a plot owner who has the exclusive right of sepulture in a plot and who is interred in that plot has made a specific disposition of the plot by express reference to the plot in the owner's will or by written declaration filed and recorded in the office of the cemetery organization:
(1) a grave, niche, or crypt in the plot shall be reserved for the surviving spouse of the plot owner; and
(2) the owner's children, in order of need, may be interred in any remaining graves, niches, or crypts of the plot without the consent of a person claiming an interest in the plot.
(f) The surviving spouse or a child of an interred plot owner may each waive his right of interment in the plot in favor of a relative of the owner or relative of the owner's spouse. The person in whose favor the waiver is made may be interred in the plot.
(g) The exclusive right of sepulture in an unused grave, niche, or crypt of a plot in which the plot owner has been interred may be conveyed only by:
(1) specific disposition of the unused grave, niche, or crypt by express reference to it in a will or by written declaration of the plot owner filed and recorded in the office of the cemetery organization; or
(2) the surviving spouse, if any, and the heirs-at-law of the owner.
(h) Unless a deceased plot owner who has the exclusive right of sepulture in a plot and who is not interred in the plot has otherwise made specific disposition of the plot, the exclusive right of sepulture in the plot, except the one grave, niche, or crypt reserved for the surviving spouse, if any, vests on the death of the owner in the owner's heirs-at-law and may be conveyed by them.
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