This is out of my area of expertise so I suggest those interested in the primary question do additional research.
Is your fiancé receiving survivor's benefits because his father died before your fiancé's 18th birthday, or is he receiving disabled child benefits because he was found disabled before the age of 22 and his father died, retired, or became disabled?
It is my understanding that if your fiancé is receiving disability benefits because he was disabled before age 22 and his father died, is retired or disabled, your fiancé's benefits will cease upon marriage. "What happens if the adult child gets married?
"If he or she receives benefits as an adult disabled since childhood, the benefits generally end if he or she gets married. However, some marriages (for example, to another adult disabled child) are considered protected."
If the fiancé is under age 18 he may be eligible for survivor's benefits if he is unmarried or less than 19 if he is a full time in elementary or secondary school. (See https://www.ssa.gov/pubs/EN-05-10008.pdf
) Again, this is not my area of expertise so it is advised that anyone in circumstances described in the original post of this thread contact SSA for guidance but it appears the original question may be moot if the survivor [in high school and under age 19] or the beneficiary marries. (NOTE - survivor and beneficiary are two different terms with two different meanings.)
Social Security Disability Insurance (SSDI) benefits for adults disabled since childhood The SSDI program pays benefits to adults who have a disability that began before they became 22-years old. "We consider this SSDI benefit as a “child’s” benefit because it’s paid on a parent’s Social Security earnings record.
"For a disabled adult to become entitled to this “child” benefit, one of his or her parents:
"• Must be receiving Social Security retirement or disability benefits; or
"• Must have died and have worked enough to qualify for Social Security.
"These benefits also are payable to an adult if he or she is disabled at age 18, and if they received dependents benefits on a parent’s Social Security earnings record prior to age 18. We make the disability determination using the disability rules for adults."