How can Guest User License (Sites) create a record that is Controlled By Parent into sharing rules?

I have two custom objects, one of them is the parent of the other and I need to create a record type of the child (Into the guest profile I check Read and create of the child object) but when I try to create it, the following error raise:  "INVALID_CROSS_REFERENCE_KEY: Record Type ID: this ID value isn't valid for the user " and that is because the child object is in "Controlled By parent" and for the default, the  "Secure guest user record access" is checked and it means that the child object has "Default External Access" in private by default and I CAN'T change that.

#Guest Users  #Sharing Settings  #Controlled By Parent