45 CFR §2552.82

1. (a)Only when a Foster Grandparent has been assigned to, and has developed a relationship with an individual with a disability, may that assignment continue beyond the individual's 21st birthday, provided that:
   1. (1)Such individual was receiving such services prior to attaining the chronological age of 21, and the continuation of service is in the best interest of the individual; and
   2. (2)The sponsor determines that it is in the best interest of both the Foster Grandparent and the individual for the assignment to continue. Such a determination will be made through mutual agreement by all parties involved in the provision of services to the individual served.
2. (b)In cases where the assigned Foster Grandparent becomes unavailable to serve a particular individual, the replacement of that Foster Grandparent shall be made through mutual agreement by all parties involved.
3. (c)The sponsor may terminate service to a child with a disability over age 21, if it determines that such service is no longer in the best interest of either the Foster Grandparent or the individual served.