Well, not technically SD, my partner's DD, but it's just an easy acronym.
DP and I have been together 7 months. For various reasons he met my children (10 and 14) fairly early on and he has developed a great relationship with them. We formed a household for lockdown, again for various complex reasons, but it's all worked out well. He lives nearby so he does his child contact at his place as we didn't want to force a 'family setup' on the children too soon. We have had the opportunity to run this situation past the police who are more than happy with our risk assessment so please no "BUT LOCKDOWN THOUGH!!" responses. We're trying to do the best for everyone in a complex situation.
His children are 14 and 12. His son, the eldest, and I get along great. He's a dry and quirky soul, pre lockdown we had taken him along on a few activities with my kids and had a great time. On these occasions his daughter had declined the invitation to come along. DP also has a 14 year old stepson who calls him "Dad" and who he is still very involved with - he separated from the kids mum when they were very small and raised his stepson for 9 years, and as far as I'm concerned he is as much DP's child as his bio children. The stepson and I have also met a few times and get on well, and I've met his mum when they dropped gifts over on DPs birthday and she's nice and we got on ok.
We've attempted gradual introductions with her and I, but the difficulty that we face is that her mum is VERY hostile. She has repeatedly told SD unpleasant things about me that are not true. She has given SD some completely inappropriate and explicit information about mine and her fathers sex life, again not all entirely accurate, but none of which should be divulged to a 12 year old. This has resulted in SD being very hostile to me and my general existence, and although she seems to have softened a little, she still very monosyllabic and sulky in my presence. I'm not necessarily blaming her for this, she's been through a lot and she just a child.
Her home life is very complex, SS are involved due to DV between her mum and her now ex partner, her mum isn't the most stable of influences and DP does what he can and tries to have them as much as possible but it's all on mums say so. I think the softening in her attitude is related to the fact that on a few recent 'incidents' I have been there when she's been picked up late at night by DP due to arguments or aggression and I've done my best to stay in the background but be supportive. I've bought lots of nice 'girly' toiletries etc for her to use at DPs house, and a snuggly hoodie of her favourite TV show to wear when she watches it.
I guess what I'm saying is that I know this has to be done slowly and on her terms, I'm not planning to force myself on her, but if really appreciate any advice on helping her understand that I'm not the heinous bitch her mother makes out. Either that or some words of encouragement from anyone who faced a similar situation but is further down the line and can offer me some hope. DP and I don't plan to rush into anything like moving in together for a good long while yet, but it would be nice to now that a few years down the line, it would be possible, and I want to slowly build a solid relationship with his daughter so that we can do that in the knowledge that everyone is happy. Or even just plan days out etc, with the five children, and know that they are all happy to be there.
Sorry, this is a bit of a stream of consciousness and I've probably missed things out, I'm happy to answer questions but please be gentle. I just want to work towards everyone being happy.