我们父母身上都有长处和短处。

What's the meaning of 身上 here?

"on the body" ?

So I would guess it to mean their physique /outward appearance has good and bad sides.

Mnnnn, "on the body" seems too literate. There is nothing like it in English. figuratively speaking...for our parents as human beings....something radiates from inside out, not merely on the appearance.

“themselves”

pts,

So it's part of the pronoun, 类似的“我们父母他们……”?

So is this about their character qualities then?

That 身上 is added for emphasis. So I translate it as “themselves” to make it “Our parents themselves…” Another way to say it in Chinese is 我们父母本身。。。

Its usage is similar to 这件事包在我身上，保证兑现。Searching the web for the translation of 这件事包在我身上, I’ve found something like, “leave it to me” or “just leave it all to me”. That 身上 never gets translated because it just emphasizes the “我”.

I can’t see any reason why it’s limited only to character qualities. Any intrinsic quality, like physique / outward appearance can be counted.