I daren't post this in AIBU but I want opinions on this please, my partner has a child with a previous girlfriend (never married) of 5 years (split 10 years ago) his DD is the youngest of four siblings who all have the same mum but three different dads, the other dads have never been involved, after they split my partner continued to treated her other children as his own. When we met 3 years ago he told me he had 4 kids, then quite soon afterwards told me that only the youngest is his but they all call him dad. All apart from the youngest they are adults now and still call him dad.
I have 4 children with my ex husband, I feel that by referring to these kids as his own he somewhat diminishes my experience of having given birth and brought up 4 kids of my own, when we're out he would tell people he has 4 kids and I might say and I have 4 kids too but I feel as if even though he's done a great thing by being there for his ex's kids they aren't his kids and it's not the same as me saying I have 4 children.
Please help me understand why I feel slighted by this, I'm probably being massively unreasonable hence posting here rather than AIBU