Step-families are now becoming more common in our society. The merging of two families can be really difficult for everyone concerned. This is even more difficult if you are living with your step-family and it is natural that most teens will find the adjustment period extremely uncomfortable. There is no magic timescale for when this will pass. You all just have to work through it together.
One worry that is perfectly natural is that you will lose your special relationship with your parent due to their new relationship and any other children that have now become part of the family. Hopefully your parent has fully included you in the process. If not, try to have one to one chat with your parent and explain your fears. Tell them how they can best support you to deal with all of the changes.
You may decide that you are not going to have anything to do with your step family because it was not your decision to become involved with them. However, it might actually be best to give them a chance but you don’t need to rush it. You never know, you might actually like them and soon consider them an important part of your life. Also remember that they are going through the same changes as you are. It might be that you are never friendly but if you can find a way to co-exist, it will make it easier for everyone in the household including you and your parent.