What cruel and unacceptable behaviour!
Even if there’s more to it and you’ve done something to offend them (such as rudeness or demanding the same amount of money they’d given your sisters for deposits, even though you didn’t really need it) it’s really horrible to take it out on their GC.
Have you tried talking to them all individually, i.e. each of your sisters? What was your relationship with your sisters like before? Maybe your parents have lied or exaggerated to your sisters about something you’ve done or said. Or maybe your sisters feel beholden to them to continue receiving their love, support or money.
I suggest you try speaking to them all individually. Ask to meet in person and ask whether they no longer want a relationship with you and your DC. If they do, what do they feel needs to be done (and by whom) to make that happen. You don’t have to respond immediately. Listen and consider what they say. If they don’t, say you’d like them to have the courtesy to explain why.
If they won’t respond to messages asking to meet, send an email or letter to that effect.
If you still get no response, there’s nothing more you can do. So, seek therapy to deal with it. Being ostracised from one’s family (what it’s now fashionable to call ‘no contact’) is very traumatic. You need to recognise and work through the trauma.
It’s always better to want to reconcile, resolve differences and move forward positively, with love and kindness. Unless, of course, it’s dangerous (e.g. risk of psychological or violent harm). But some people don’t have the maturity or kindness of heart to do so. The silent treatment is a form of abuse. It tends to make the abuser miserable deep-down, as they have to live with it. But, like most people who behave abusively, they tend to employ DARVO: justify the abuse to themselves and victim-blame.
Ultimately, you can’t make people behave in a certain way. You can only control your response. Set your own standards for yourself, rather than allowing yourself to be dragged into retaliation. Remain mature, open and kind. If people don’t want you in their life, see it as their problem and their loss. Remove them from your social media, so you can’t see their posts. And find people who do love and value you and do want you in their life. Life’s too short to allow people who’re petty or abusive to affect it 💐