Spouse and a totally disabled child. Recommend you talk to local veteran's agent. Space is not a problem, ample space.
"Burial benefits available for spouses and dependents buried in a national cemetery include burial with the Veteran, perpetual care, and the spouse or dependents name and date of birth and death will be inscribed on the Veteran's headstone, at no cost to the family. Eligible spouses and dependents may be buried, even if they predecease the Veteran." https://www.cem.va.gov/burial_benefits/
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