DP and I live together with my 3 DC.
DC spend a fair amount of time at their father's house.
DP and I have been together for two years.
DP doesn't really get involved if I need to discipline DC. If they are really misbehaving (not often) and are not listening to me he may step in and raise his voice at them.
If they are being unkind to each other and I'm in another room he will step in and stop the fracas.
DD (10) has told ex she doesn't like it when DP tells them off. Ex has told her to let him know if he does it and he will 'punch his face in...'
Aibu to think that DP does have a right to discipline to a certain extent as we all live together?