Stepchildren

My husband has two children one 17 biologically his the other 19 not biologically his but he claims her. They are from the same mother and she already had a child, then the one he claimed while she was pregnant then the biological child. Then this same woman had another child by another person so thats 4 fathers. I say this to say she has threatened child support more than once for the two despite one not being his biologically. That is a low thing to do because he didn't have to claim her.So thats that then my husband was locked up for 16 years so they didn't get to have a relationship. So I met him shortly after he came home and we got married. So now the only time the almost grownup kids call is for money and sometimes one doesn't ask she cash app for everything from gas to clothing at least twice a week.They ask for money at the last minute and it be like $150 for shoes or to get her hair done. I am a grown up and I don't spend money like that. Sometimes they get it and sometimes they don't. Now I understand he missed out on everything but the sins of the father and the mother shouldn't befall on me. They have a sense of entitlement and aren't humble and very rude. We honestly don't have it to be handing out money every time they ask for it. A man is supposed to provide for his children but not at the expense of your home where your wife lays.I have told my husband that he needed to set money aside for them each month besides the money he gives for there phone bill but maybe give it to the mom to do with it whatever she see fits which meant him working overtime to do this from time to time if needed. So instead he works overtime time to time but the money is going to something else that he really wanted. Then not to count that I have a child the same age as one of the stepchildren that doesn't ask for anything and is always getting the short end of the stick.We are also expecting and have TTC for a while now. I am super excited but super worried at the same time. I already know once he tells them the news they are going to be bitter. I would be mad too if my dad missed out on my entire childhood but at some point they need to understand that both parents are at fault. There mom lived a lifestyle that she loved and she had no problems with it and because of there bad choices there were consequences. So he makes comments like you know all the kids are going to be jealous of the baby and we have to be careful not to spoil the baby.So what does this mean for this child. Do I have to hide our childs life from his siblings. I shouldn't have to worry about money or his past sins. I love my husband but this is a major issue and it can't be taken lightly. Any advice ?