What Is Expected of Your Extended Family?
This could be a concern for all of your family members. How are they supposed to treat your stepchild? Should they prepare gifts for your stepchildren for the holidays? What if your grandfather gives all of his great-grandchildren a car for graduation? Does this hold true for your stepchild as well? Will they be babysitting your stepchild? Will he be over every weekend? Can they reprimand him if he misbehaves? At first, it will probably be awkward, and they won't have any idea what to do with him; and he might not have any idea how to interact with them. Your stepchild's age and the relationships he has with his biological family will both play a role in the way he interacts with your extended family.
According to the State Department of the United States, the extended family is defined as a family that includes three or more generations. Normally, that would include grandparents, their sons or daughters, and their children, as opposed to a nuclear family, which is only a married couple and their offspring. Families often have their own interpretation of extended family and include very distant relatives and ancestors.
If your stepchild is quite close to his biological family and your extended family is more of a secondary family with whom he doesn't regularly interact, they will not be as involved in his life. Any expectations of your stepchild having a relationship with them will be minimal. However, if your stepchild does not have frequent or consistent contact with his biological family, your family might become his primary extended family. Either way, your extended family is likely to take their cues from you. If there is a holiday party and your stepchild is coming with gifts for everyone, let your family know this ahead of time. It isn't rude, but actually helpful for your family to know that you are expecting them to take him in as one of their own. For a stepchild who is not around frequently and mostly engages with his own family, gestures like sending cards for certain occasions and inviting him to events might be all that you can expect of your family.
The age at which your stepchild becomes a part of your family will also impact how involved he is with the family. A child who is young will most likely see family more, as he is forced to go where the adults in his life go for the time being. As children age, they become more independent and don't necessarily need to go to Aunt Betty's birthday party. An older child or teenager might not have much interaction with your extended family, and it is not something that needs to be forced upon either party. Regardless of age, a child who has experienced multiple marriages and divorces by either parent is not likely to be quick to bond with your extended family. He might think it is pointless to engage with any family members, as he might see them as temporary. A child who has this type of experience should be given plenty of time to feel comfortable forming relationships with family members. It might take years, but it is important that you do not push these relationships. Forcing him to hurry up and create a bond will create a sense of urgency that is unnecessary if you are planning on staying with your partner forever.
For the comfort of everyone, be clear with your extended family on what your expectations are and have patience, as this might be a new type of relationship for them. Encourage your family to treat your stepchild as they would any other child, keeping in mind that special treatment can also make him feel out of place.

