"Anyone can propose a merge of duplicate profiles. You also don't need Pre-1500 Certification to approve a merge. The standard rules on approvals apply."
https://www.wikitree.com/wiki/Help:Pre-1500_Profiles#Merging
My guess is that you are trying to do some other sort of editing at the same time, which you would not be certified to do. What exactly are the steps you are taking?
Also: Swynfen-5 was born in 1577, and Swynfen-3 was born in 1425, 150 years earlier. In what way are these duplicates of each other? Vernon-160 would have been 14 at the marriage of Vernon-25, which of course is possible in that era - but do you have a source which shows this early marriage?
Darlene, I checked Swynfen-3......merged as requested. I, then, approved Vernon-160 into Vernon-25.....now, awaiting pre-1500 assistance. Thankyou.