I suppose this implies that your stepfamily is broken and urgently needs some help.
How you can fix this family will depend greatly on how much it is broken and how long it has been broken.
There may be no quick fix, but will require some time before things get back to normal.
First off what have been the main problems. Have you sat down with your partner and discussed this with them.
Have you thought about seeing a family counsellor.
Do you have any support, even online support for example the Stepfamily Zone forums .