I have encountered this to some degree, I guess. I've had some people who have struggled with find one person worth loving make comments about my having two people to love who love me back.
I haven't let it get to me, though. I am far from perfect, but I've worked really hard to get to a place where I was mentally ready and healthy enough to be in a relationship. Just before I met my husband, I'd reached a point of realizing that settling was far worse than being alone - and I'd decided there would be no more settling for me. He and I had a rough first year, but we worked through it, and were all the stronger for that work.
I have definitely had female friends who were incredibly envious of my relationship with him. He's an amazing guy... also not perfect, but closer than most
. He makes me laugh when I want to cry, he's been my partner through a lot of loss and trouble, and without him life could never be as sweet. So, I guess what I'm saying is, I get the envy.
We added our girlfriend to this, and well... most people just don't get it. Generally speaking, the reactions have been, well, if you're happy, I guess that's good. Which is probably the most positive reaction I could expect from most people. I guess "coming out" made me realize that I had some really good friends, because I was worried more of them might decide to distance themselves or walk away because of our GF.
So, when I see someone who is envious, it just reminds me of how much I have. While I often say that I am fortunate, I also know that I've worked really hard to maintain my relationships. The one with my husband hasn't needed much "work" since that first year, but *I* had work to do even after I met him to feel worthy of love, worthy of a healthy relationship. Now, we're all working to try to make the triad something that can grow and develop into the sort of rare bond that my husband and I shared before her (and still do separately from what we share with her, if that makes sense).
I guess my point is, happiness is not something we're just given. We work to be happy. It's foolish to think it can just fall into your lap, no matter how easily love comes to you. It's also foolish to think that you can love and be happy when you don't give it 100% of who you are. So, in regards to outside envy, I just see it as, well... I've worked hard to have what I do, and I'm very fortunate that I was able to see things I needed to do in order to be healthy enough to find this sort of love, and I'm very thankful that I have a partner (now two) that loves me enough to be there for me while I continue to grow as a person, and as a partner.