I really don't know what to do about this.
I am in my mid 40s and am friends with a couple who are also in their mid 40s.
Over the 10 years I've known them, I've become closer to him. They both have different hobbies and interests, he and I have similar hobbies and interests. His wife actively supported and encouraged his friendship with me so that he would have someone to do these things with. We are both a little 'quirky' (apparently) and the general lighthearted consensus has always been that if we are friends doing this shit with each other then no one else has to...
There is, and never has been, anything untoward between he and I - their relationship hugely predates our friendships. I have no reason to think he is interested in me; I'm certainly not interested in him; he loves his wife very much; he's not my type; there is no flirting... you get the picture. We're just really bloody good friends. He's like a brother to me - we have a laugh, get on well and I trust him implicitily. We're just very comfortable with each other precisely because there is no 'sexual tension'.
I'm aware that, over the years, this has been questioned by some people who think that something must have happened or must be going on between us.
We do a hobby together. I've been 'probed' about our friendship by the women in the group and he told me the other day that the men had asked him similarly. All the members of the hobby group are married (except for me) to other members of the group or spouses who support their hobby. His wife rarely turns up to these things (for her own reasons, which I understand) but she has done, so everyone has met her and everyone has seen the three of us together.
But a comment was made recently which made me realise that their curiosity is still there and, in a couple of cases, I have begun to sense a feeling from them that our friendship isn't 'appropriate'. But it really just bothers me if people have just drawn their own conclusions that we "must have 
" As much as anything, 10 years down the line, this feels a bit tired now given it seems to be everyone who wonders it.
I don't want to lose my closest, and now oldest, friend but neither do I want his wife to be hurt by unfounded suspicions. Even though she knows they're not true, it's got to hurt knowing that people are saying stuff. I wouldn't like it if people thought I was being a mug, I guess.
I suppose I don't really have anyone in real life to talk this through with and just wanted some feedback.
For clarity, we have spent a lot of time together over the past 10 years as families - holidays; Christmases; birthdays... our children are friends... As the children have grown older, we have spent less time together as whole families - it does still happen, just far less frequently.