I have read some threads recently that mock SMs for suggesting their Dsds are miniwives.
Whilst some of these threads are typed in a moment of despair or anger and may come across as jealous or hateful, living with it is both detrimental to child and partner.
I only have experience of father / daughter spousification and, although this has been managed over the years, still causes tension and hostility every now and again.
Backstory: DP left Dsd18 at the age of 4 and in another country at to be with ExW, ( yes I know it's shitty & have told DP so myself).
DP left ExW when Dsd10 was 4, (reoccurring theme, I know), and the guilt of his first breakup has followed him. DP has said he regrets leaving Dsd18, although they are building a relationship now.
From the age of 4 till now DSD10 gets told she is the most important little lady in his life. I don't particularly like that as DP does have an older female child.
DP had 4 yrs of non-stable relationships, non of whom were introduced to Dsd10 and effectively they existed as a single unit. For part of this time DSD10 also lived full time with DP.
DP has deferred to Dsd10:
What car he drives. Expensive convertible, soon changed for something more practical.
Our first home. I didn't realise DP had already viewed it with DSD10 and found it acceptable.
Family pet, again a stealth viewing.
Things have got better over the years but DP does occasionally defer adult decisions to Dsd10, instead of discussing as a family or as adult choices.
DSD10 does sometimes see me as a rival for DPs affection, even though it is a totally different type of love. ie: DP cannot touch or be near me when Dsd10 is here. DSD10 will actually kiss DP and then check to see if I'm looking and smirk.
Dsd10 will want to check any items we are buying, sofa, car etc. are Ok.
DSD10 must be sat next to DP, holding his hand & being spoon fed at any function that requires eating. Any other female s that approach are given lasers, including DPs own mother!
Tbh, I just leave them to it now as DP is oblivious & I enjoy the peace & quiet.
It has taken me some time to realise that DSD10 is probably jealous of the affection between myself & DP and I am better off leaving them to their own relationship, however I know many SMs will notice a significant change in their DPs behavior towards them when Dsc are around.