Translation:Ei lygaid o
There appears to be some inconsistency about whether this translation is correct. Here I was marked wrong for not including "Ei lygaid" as a translation of "His eyes". In another question I was marked wrong for putting "Glas yw ei lygaid" rather than "Glas yw ei lygaid e" as a translation of "His eyes are blue".
The question that you refer to has now been corrected - the second pronoun is now optional in that pattern.
Both "Ei lygaid" and "Ei lygaid e/o" are accepted in the database for this sentence. The "Ei lygaid" part is mandatory and the "e/o" is optional, but adds emphasis.
And clarity as to the gender of the owner of whatever it is being discussed. If it happens again, I'll screenshot it.
The "e/o" doesn't add any extra infomation as to who the posessor is as it is clear from the mutation here. i.e "Her eyes" would be "Ei llygaid".
What I meant was that, depending on what is being owned, adding the following pronoun can sometimes be needed to clarify the gender of the owner. I agree that in this specific case it is clear. As it would be if we were talking about cats or cars, for example.