So My SO and his 1st Kids Mom are pissing me off!! Am I wrong?

Ok so SO has 4 other children by another woman. I also I have my own 4children not counting my bump now. I'm doing good for myself have my own everything and take care of my children without having to ask their fathers for anything. Well it seems as though his ex feels like I have to take care of her and her children because I'm with him. He recently lost his Job he was giving her $400 a month and throughout the month she would still call him whenever she needed money for herself and he would give it to her. So today she tells him that her lights are going to get cut off and she needs $115 knowing he doesn't have a job but age expects him to get it from me because she feels "I can afford it" um excuse me but I can afford my bills not yours your a grown ass woman. He told me she feels like if he is living with me and because we live in a nice brand new house her and her kids should also reap the benefits. I'm sorry but I worked for what I have! Where do these woman get off thinking shit like this. He constantly asks me for money to give to her or to buy something she claims her children need and if I say no its an argument. I cant understand their logic. Hell over the summer I took ky kids to Disney World and she was pissed because I didn't take their kids which caused confrontation with me and him. I'm by no means a sugar mama hell he is older than me. I cant help it i f I never have to work again a day in my life but me and my children are going to be ok either way. And yes she is on all kind of assistance government wise I'm not knocking it but if u want better you have to get out and try to do better rather than relying on others. Am I wrong for feeling this way you guys.?