I don't think it's polite to speculate on the relationships of others but I will say this about the ep on marriage:
There's certainly statistical evidence enough to show that marriage is still popular. It's popular enough that gay rights activists wish to have that legally binding contract. It's useful if you have kids and cuts down on paperwork (and confusion when there’s a parent-teacher night - as I can say with my own anecdotal evidence!).
I think (and feel free to say otherwise) the point was being made in the ep that it's silly to think that the notion of monogamy being a natural state between humans?
I personally feel that if my partner died (and sadly, I think - and may be wrong again, feel free to show me evidence otherwise - that men are more likely to die than women in a marriage, generally from old age? and therefore I may have to face that) that I'd be bloody devastated but wouldn't rule out the likelihood of finding love again. And I'd sincerely hope the same applies to him if I was dead or if we were divorced. Life is too short to spend it alone without a state of either marriage or friendship or kinship or whatever!
Have a look at how many people remarry. Or divorce. Or have multiple relationships with many partners when dating. Or even have two or more steady or interchangable partners (either unaware of each other or maybe even totally aware and fine with it!). I've got a book here, "Sex with Kings : 500 Years of Adultery, Power, Rivalry, and Revenge" by Eleanor Herman [review: rather lightweight, gossipy but was breezy enough to read at the beach] which outlines relationships where multiple partners for the monarchy existed. Certainly during periods of history it was condoned and even encouraged. Things changed, of course (look at Camilla Parker Bowles and people's attitudes to her) but it still happens.
Anyway. I think my point is that it's absurd to think that marriage is some sort of 'bite my thumb' at multiple-partner relationships (by which I mean being a person who commits or has relationships with more than one person during their life, not necessarily a polygamous person). I'd say that it's a message of commitment but doesn't necessarily mean that I or others are ignoring the fact that circumstances may change and affect a marriage (death, divorce, finding some hottie to share the bed and house with...) or that humans are in any way different to other animals. We're designed to 'spread seed' and marriage is one way to do it but doesn't mean that it's the only way.
Why not just say 'best of luck to them'? Or better yet, ask them yourself by raising it as a question on the P&T website, because you may get an answer there - I don't think you'll get one here.
(Edited to correct spelling error - and to add that Cancerwoman pretty much said it already with more eloquence!!

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