Possible to make a child layer's field mandatory based on a field value in the parent layer?

[9ls1]

I have point layer (parent) with a child layer (a table for saving images).
When digitizing a point, the user fills in several fields and has to take two different images 'pic_plot' and 'pic_plant'.
In addition, she/he has to take another photo if field 'name' = 9 in the point layer. E.g. if 'name' = 9, then the user must remember to take 1-3 pictures (i.e. at least one photo, maximum 3 photos). If 'name' != 9, the user shall not take any images. I have tried several expression. However, it seems like the 'name'-field is "empty" (NULL) until the point actually is saved and therefor I cannot use 'name' = 9 in the condition? Is there any (other) way of achieving this?
https://gis.stackexchange.com/questions/447779/get-attribute-value-from-parent-layer-to-child-layer-sharing-same-uniqueid?rq=1

point layer (parent)
...
name
rb_id (uuid)

photo layer (child)
pic_plot
pic_plant
pic_name (Is it possible to make this mandatory only when 'name' = 9?
b_id (uuid)

Points and photos are connected through rb_id = b_id.