No, it because I used a multiple follower glitch, first you bring your follower of choice, in my case Teldryn, to where Serana is, I joined the dawnguard so she's at fort dawnguard for me, then I place my follower really close to Serana, dismiss him and quickly back out of the conversation, and then quickly talk to him again and re-hire him, quickly back out of the conversation again and talk to Serana and ask her to follow me, if this is done fast enough, you will have both a follower and Serana with you.How did you get Serana in a house? Can she be married?
This can also be done with the dark brotherhood initiates and Cicero (all 3 of them can be made your follower at the same time), making it possible to have a total of 5 followers.