In the interest of clarity, I would like to see questions about adoptive families and blended families avoid the use of the term "real parents", especially as a euphemism for biological parents.
In genetic genealogy, the term NPE refers to the situation where the DNA no longer matches up to the expected surname, for whatever reason. This is not always a case of adoption or infidelity -- sometimes changes in surname occur because of social reasons, e.g. a man taking on the surname of his wife's family by legal arrangement so the surname won't die out, or a man taking on the surname of an admired clan leader.
NPE is sometimes parsed as "non-parental event", but some people (including yours truly) prefer "Not the Parent Expected" (not predicted by the DNA results). In a recent webinar "Using DNA with Your Study" presented by The Guild of One-Name Studies, Maurice Gleeson estimated that the number of men whose Y-DNA doesn't match up with the surname they have is likely to be roughly 50%. (His back-of-the-envelope estimate was between 40-60% which he expressed as 50% in the interest of brevity.)
On this website, we will continue to have questions about both paper-trail research and DNA research. Most people assume biological relationships for parents and children unless proven otherwise, but the reality is that for specific, individual cases, we just don't know.
Can we try to make our questions as clear as possible? If we need to refer to a biological parent vs. a step-parent or an adoptive parent, can we just say plainly what we mean? "Birth parent" is one term which is used in an adoption context to distinguish the biological parent from an adoptive one. "Bio-dad" or "bio-mom" is a less formal alternative.
We are family historians and genealogists. Many of us do DNA research as well as paper-trail research. We are all aware of how children come into the world. Euphemisms do not become us.