Okay, I know some friend of friends, who did with this their Ex. Still co-habitated together in the same home, even if divorced. They were amicable and, they were still with their child.
Then, the woman found a boyfriend. They were all in love. Just like you. He met her child etc. All fine and dandy. And it was fine with the Ex, and the Ex had had his own life by then too, and a Girlfriend.
But well, even if their daughter was so social and gregarious and seemingly "fine" with it and all these relationships around her... she started to have behavioral problems. Really, unpleasant ones and in school too. This was a 7 year old. The Mom, moved in together with her Boyfriend etc. And then, one day SHE got pregnant with the Boyfriend. Long story short, her daughter is a mess. Now. And that baby with the Boyfriend, was born already.
And her relationship with her daughter, is a mess. Too. Now. ie: she and the daughter just do not get along anymore, but the Mom acts like it is only the daughter's problem. She does not see, that her life choices, IMPACTED her daughter in a bad, way. Meanwhile, the daughter is a mess and a problem... everywhere. In school, at her extracurricular activities, at home, with family, etc. And so now, the daughter is seen as a "brat." But it is not, the daughter's fault.
And the Boyfriend, is all stressed with 2 kids. One not being "his" even if he really likes, her daughter from a previous marriage.
And because they are not married, (but they were supposed to get married, but they have not yet married)....
they are having problems now. It is not all peachy. Nor for either of the kids. And, the Mom of her Boyfriend, does not like her or her kid.
Many problems!
And meanwhile, her Ex.... is now not seeing anyone. So his Ex-Wife, unloads "their" child onto him. For babysitting. So she can have her "life" with her Boyfriend and "their" new baby. So the Mom's other child from her Ex Husband... is like a ping-pong ball... going back and forth between her/her Boyfriend's house... and their ex-house, that they USED to share, together. And sometimes, the woman's Boyfriend, does not even want... her daughter from the Ex-Husband around. He tells her to send her to the Ex-Husband to "babysit." Oh but sure, the Boyfriend supposedly likes/loves her daughter from the Ex-Husband. But her daughter is now a "brat" and problem child. Remember? And it is all because, the Mom chose her Boyfriend, over her daughter and changed where they live and how they live and now a baby from the current Boyfriend, is around. Too. The daughter from the Ex-Husband, doesn't even like the baby from the Boyfriend and doesn't even care if they are supposed to be "siblings."
What a mess.
And the other mess of it all is: everyone in their city, knows about it and "why" her daughter is such, a mess. But that doesn't mean they sympathize.
You cannot expect, a 4 year old, to fully understand these things, nor to adapt to it, nor to permit it. They cannot decide their lives, for themselves. They are too young.
BUT a child WILL reap, all of the repercussions, from it.
Negative repercussions.
Like another person said: why don't your Boyfriend... move to where you and your daughter are????
Not you move to him. 3 hours away.
And then how will the Dad/your Ex, see your daughter?
And without having to switch schools etc. or move, too?