There was a rejected merge with Kilpec-6. Note by the way that I've been editing both profiles, so they looked different when that merge was rejected.
Kilpec-6 is certainly a real person who can be confirmed with good sources, and certainly the same person some of the Mare-127 article is about. The real difference is that it is another style of profile. (That the dates were different seems irrelevant on articles like this. That reason gets used wrongly to block merges too often.)
Mare-127 does not look the same as Kilpec-6 because it includes things with no good source: extra people, and the equation of his family to the De La Mare and Dene families. So to be frank it is different because worse.
What to do? Wikitree does not like deletions. Merging in this case would be a lot of work and a worse result. One option is to make sure the Mare-127 family is tagged as problematic and disconnected from any real people. Another theoretical option is still merging, but then what if anything should we keep from this profile?
I propose that with Kilpec-6 which is clean and correct and easier to improve; and quarantining Mare-127 and most of what is connected to it. But feedback would be welcome - especially if it involves good sources.