I don't think there are usually gatekeepers at funerals unless it is a small closed funeral with only specific invitees or just family - in which case around here that is mentioned in the notice/obit. I have never gone to a funeral where anyone was checking. I have been to some rather small ones where a stranger would be noticed but I never saw anyone try to throw them out or anything --more like musing "I wonder who that is and why are they here" sort of thing.

Having had some whacko client families which included therapist offspring/siblings - I would caution someone to ask themselves how are they going to feel if the family dynamic is not what one expects. I have had several client (my client would be a sibling or parent) families who hated their therapist sibling/offspring and vice versa. I always found it fascinating but I wasn't emotionally invested in any of it. I admit to getting a kick out of how dysfunctional the therapists often were.