Wason is a little out there and doesn't fit with the theme, but I know it is honouring so it can't be helped.
Thaddeus and
Phineas go great with
Josephine,
Thomasina and
Edda. The only thing I might be picky with is that they are vaguely rhyming, which I dislike to see in twinsets. I might tweak it to something like:
Thaddeus and
FinneganPhineas and
TheoThaddeus and
FinnianPhineas and
TudorThaddeus and
GideonPhineas and
Gideon(I know
Gideon does not seem related at all but it was just an inspirational brainwave)