Sorry to post on a mums site, didn't know where else to ask.
I am a dad to an 13 year old girl, DD. I split from her mum when she was 3 because ex wanted more children and I didn't. DD lives with her mum round the corner, Stepdad who I get on well with and her 3 siblings. Ex and I co-parent well, I pay £100 above CMS rates, half her school uniform, all her clothes for my house (which get swapped between houses anyway), half school trips etc. I also pay for her phone contract. I attend all school related events. i see DD every other weekend and 2-3 times in the week depending on what she's doing/where she wants to be. I also take her away on holiday for 2 weeks at Easter (she goes with her mum, SD and siblings in the summer so I don't interfere or try and plan it for then). She can easily walk between our houses and will often pop in to "pick something up" from her room here. I'd say we have a great relationship, I text her between visits and she knows I'm always here if she needs me.
DD has come to me today and asked for me to sign the forms so she can have the same surname as her mum, stepdad and siblings. She still wants to see me and spend time with me, still wants me in her life. She calls her Stepdad by his first name so he's not trying to take over, he's actually a really lovely guy and we get on great.
I am crushed. Part of me wants to say no. But I don't want to push her away. She currently has my surname, as ex and I married before I was married and ex took my name before she married her current husband whose name she now has.
Oh god I sound so selfish don't I? I don't want people assuming her Stepdad is her father, I am her dad, and always will be.
WWYD? Say yes and sign? Or say no?