I have an image of Una rubbing her hands together in glee at this discussion, thinking "It worked! It worked!"
Personally I'm on the side of "a very close relationship of support and affection and dedication, but not necessarily romantic or sexual as we would understand it." But as I said earlier, I'm perfectly happy to let the ambiguity stand. If they are romantic, that's lovely. If they're just two older men growing comfortable with each other as they age, that's fine too.