Can a family member write a detailed letter or to help with my son’s PS case or does it only have to be from a neighbor, specialist etc?

My mom finally witnessed what I go through on a daily basis and never sees anything with her own eyes or in person only through videos, pictures and FaceTime. She finally got to see and experience what it’s like to be OUT with my son! lol she was so shocked and could not believe what she had just went through! I felt so bad for even getting her involved because she is not young and can’t run too fast and has a bad bad knee and bad arthritis. 😭 My oldest son is also the only one that lives with me and knows exactly what I go through and has witnessed many many incidents. So yeah, can they write a letter or no?