Is it normal that i feel like i don't have a family?

Of course I'm asking this at Christmas time haha. Every year during the holidays I have to visit with my family. Only my situation is a little peculiar (or familiar if your parents are divorced).

In a manner of speaking, I have multiple families. My father is married to a demon, my step mother (no really, she's horrible). I have hated her since her and my father married and she's an all around awful person. I'd go into detail...but that would be quite a few details. Her family isn't related to me in any way (her children are from a previous marriage), and I simply share nothing in common with her children. They are not nearly as bad as she is, but they are much older than me and they view me and my dad as invaders to their family. I am also pretty sure that my stepmother has been telling her children that I'm a devil spawn or something of the sort.

On my mother's side things are a little less eventful. However, family gatherings are usually dominated by other families (such as my sister's husband/brother's long time girlfriend). I have nothing but positive things to say about both families. They have never been anything but warm and open towards me.

But I am saddened by an inescapable fact about these people. They don't share my last name and the vast majority of them do not share my blood. My brother and sister on my mother's side are only half related to me (children from a previous marriage). While I am glad that their families (unlike my stepmother's family) generally treat me as a guest, I know I'm not really one of them.

I am the last person in my entire extended family on my father's side who can (at least traditionally) carry on the family name, and it makes me feel so alone. One day, I'll hopefully have a family of my own and things will be different then, but for now I feel like I'm a product of a failed marriage and not to sound dramatic, but the last of my name. There are no more (my last name)s. Just me. I love all of my family. Even if they don't have my last name. But sometimes I wish there were more people like me at the table or in the den. Is it normal to feel this way?

If you've read all of this thank you.