I had typed this out for relationships, but then realised it's kind of an AIBU, so thought I'd give here a shot.
I've obviously changed my username as this is rather identifying.
Bit of a backstory (don't want to drip feed):
DH's sister (they hardly ever see each other/get along) had a baby who she just couldn't look after. She never wanted him and was very quick to say she doesn't want him (the day of the birth). It's a rather sad situation (wants to be homeless doing drugs, etc. it just doesn't matter how much you try and help her she isn't ready for that) and she is in contact with none of us. None of us even know her whereabouts.
Anyway, we went through a very long process and ended up adopting him. We are his legal parents are both have parental responsibility. We are mum and dad. However, he is obviously biologically DH's nephew. He seems to think this gives him more rights... Morally, is that true? I obviously disagree with it. He's my son, I'm his mother. We are his parents. I don't understand why he has this mindset.
If we argue, he will always bring it up about how he's biologically his family, which I think is just spiteful. We are in no way unhappy in our marriage btw. It's just something that he has a view on and genuinely believes.
Morally, do you think that gives him the 'power' between us as parents??