We are not going to leave our home.
It is HER home, you moved into it. It is also her son's and her daughter's home and was [probably] long before you showed up in their lives.
We are not the ones that should have to leave.
And that is because
you had NO idea she had kids when you started seeing her, right? I honestly don't know what this statement has to do with it, other than making you sound extremely immature....
"I was playing with that toy first and you're not gonna get it from me!" You have already said she allows them to walk on her and it doesn't sound like you have any influence, period. If you and your fiancee are on solid ground, the question of who goes and who stays is rhetorical - or should be.
And it's not just the two of us we have a baby. We dont have a lot of money and have nowhere else to go.
Then having a baby was not the best decision, was it? I'm betting her son and daughter think she is a fool for having a child with you when you are so close in age to them. You'll have to find a way to make more money, you already said you failed one child you had. Work together at finding some options for housing yourselves elsewhere or you will fail this second child of your's too.
This whole thing comes down to one point, IMO.
You are too close in age to her kids, they will never look up to you, and you sound very jealous because you aren't 'allowed' to sponge along with them and you're not getting all the attention. Any woman who is given an ultimatum of, "It's either ME or YOUR kids" and she chooses the man is NOT a woman or mother I want to know. It doesn't matter how old or how irresponsible [she has allowed them to be], they are her kids until they take their last breaths. Mine our grown, have their own lives, but would
never be told they could not come home if something bad happened. They would also not be told they couldn't move back because I 'had a new man' (would never be one that much younger like you are; I could never handle dealing with all the crap that brings) and HE didn't want them here. Give that ultimatum to me re my sons? I'll make sure the door hits you in the a** on your way out....