What steps do I need to take in order to reconnect with my younger siblings?

My dad runs a company. He isn't good at business and not good at managing money. He doesn't make enough to afford his bills, and has for a long time been spending all of his money on keeping his office open, instead of taking care of his apartment bills.

My younger siblings are in their 20s but are completely dependent on him. They don't really pay bills and the only way they make money is through helping my dad with the business.

I want to get closer to them so they can feel comfortable opening up about their feelings on things like this, but we were all toxic to each other. Even up until I moved out last year. We would all bully each other. But it was worst for the youngest, my little brother. It was almost all of us against him. He would avoid us even though my older brother, my younger sister and I would still all go for walks around town until recently. It stopped after my older brother moved out a few years ago.

My coping mechanism for the toxicity at home was to just be numb and passive. If I did what I was told I could avoid conflict. So I'm not super close to my siblings. My older brother and I are getting closer since he's been texting me career advice. But I don't know how to approach my younger siblings.

I understand it will take time but I'm not really sure where to start. I'm not sure if a giant apology should be the first thing I text them. I'm afraid it will come off as me trying to suddenly act like a big brother now. Is it better to just slowly get closer, and apologize after we have a more solid connection? Or should I lead with an apology? I just want to be close enough instead of getting anxious. And then go be there for support, since I know how hard it is to grow up in our household where there was no support.