My DD1 was still a baby when we separated but from all my research the most important things are just keeping everyone positive about the situation and all people involved in it so sounds like you're ticking those boxes.

My DD1 is now 4 and has never been anything but comfortable with the arrangement but since she was so young it is all she has ever known really which could be why. I met DP when she was almost 2 and we had DD2 very shortly after (read basically 9 months, panic stations but luckily worked out in the end) and whilst she has memories of just the three of us (DP, herself and I), she can't seem to recall a time when it was just her and I (living with her grandparents which she also doesn't seem to remember at all) even when we speak to her about it (such as talking about when she was born and she will ask if DP was there and we remind her that we didn't meet him till later etc). I guess at the moment this is just very much her default position of normal. We are all holding our breathe for as she gets older and starts to realise lots of (most) people live with their dad (although she has in the last year started calling DP 'daddy DP') leading to questions why she (or we) doesn't(don't) as she has never really asked yet. She did go through a period of not wanting a different last name to me (I have my original surname, DD1 has her dad's and DD2 has DP's) but we all explained it to her and she seemed okay about it. Truth be told I would love to change her surname but I don't think it is appropriate to encourage or push despite her bringing it up unprompted so we just gave her the facts and left it at that, the most important thing to us is that she is comfortable.

We have always just made sure people in her life reinforce that having two homes (and two dads in her situation) is lucky and neat (grandparents etc all on board with the concept). During the week we make sure to talk about her dad like when we do things we might say you'll have to tell dad about that when you sleepover on the weekend and when she is with her dad he does similar so that she knows we are all cool with each other and her life is one fluid and joint thing rather than two separate lives if that makes sense.

In our situation, DP and I are the main carers and we make the major decisions and inform her bio-dad as such (this was agreed upon by all, we often ask him for his input but he prefers to defer to us). When we explain it to others the easiest way to describe it is that DP and I (and DD2) are DD1s family unit while her bio-dad is similar to an involved grandparent, a close relative. It works for us but mostly works well for DD1.

Every situation is very unique though, I'm not sure what will happen is DD1's dad enters a new relationship which I assume is somewhere in our future considering it has been over 3 years now but we just hope as long as we all focus on being positive then we can navigate it in a way that is supportive of DD1. DP is also terrified of the day DD1 tries to use the 'you're not my real dad' line. Plus there is probably going to be a point where DD1 and DD2 are confused about why they have to spend time apart type thing - both wanting to go or to stay. So even after the initial reality hit there can be many points that require a new investment in adjustment. I just hope even if we have difficult points that one day DD1 will be able to look back and understand it from another perspective even if she can't from her own straight away. I hope it will be obvious to her how we tried our best in a situation that was necessary so I try to keep that as my focus - it isn't just about how things are for her right now but how she will feel looking back with the extra wealth of experience and maturity behind her.

My parents are still together but I know there were things in my childhood I thought were unfair or that I couldn't understand at the time but looking back I know my parents always did their best and had my interests at heart, so when I worry about there being dark points I just need to hold onto that; this was the right decision for everyone and that will get clearer with time.