Silent Whale,
welcome to Rootschat - that's quite a first question!
Difficult. If you and your family all relate to your parents and grandparents then in many ways the name they used, for whatever reason, surely is your name? I can also see why you would want to link back to the gene pool though.
Steps and remarriages often change things - I lost my own gr.grandfather for 2 censi and eventually found his mother, who I thought had died, had remarried and the whole family were recorded under the stepfather's name. Once my gr.grandfather left home and married he was always recorded in his own birth surname and we, his descendants, all followed suit. So was there a time when a grandparent or gr.grandparent of yours made a conscious decision to stick with a different name, know it would affect all of you to come? If so, they must have had some reason.
Could you take your original surname as an extra middle name, and use it as a second given name for newborn members of the family?
I think a lot depends on the ties you feel, and the history established by, the past 3 generations who chose to be called something else.
p.s. My 'post' click collided with your new post. How much influence and affection was that stepfather held in? Sounds like it was a lot, perhaps he was someone they wanted to belong to?