Will your hens get broody? If so, you could get some fertile eggs and have them hatch chicks and just keep one of the males as his replacement.already tried. Seriously I've tried everything. All of them were adults when they met
Being raised as part of his flock it is more likely for him to accept his "son" and for the growing "son" to respect his "father".
You said you crack and check the eggs fertility but maybe he got lucky in the dark one time so you could try the incubator anyway.