1. Befriend the wife.

I'm a single man who is friend with married women.  In my case I don't want either of us getting feelings for each other.  I know it can happen if you're not careful.  So I intentionally befriend the husbands.  It doesn't take long for it to be geniuine friendship.  (It moves from being intentional to being natural.)  I usually end up closer to the husband than the wife.  As a byproduct, I've never had an issue with husbands trusting me.

I suspect if you befriended the wives, things would work out better for you. 

2. Set boundaries for yourself

Here are the ones I use:

I don't call/hang out with/etc. a married woman more than once week.

When I message or text a married woman I do group texts between her and her husband.

Pick ones that you think strengthen their marriage.  That should be your desire.

3. Be willing to let go.

If you love someone else, your focus is on them, not you.  At the extreme, if not being with you makes them happy, you'd be okay with that because you're happy to see them happy.  If you were truly focused on your friends and their wives, you'd value their marriages so much that if your friendship was getting in the way of their marriage, you'd be willing to sacrifice your friendship for their marraige.  The easiest example is if either of you started developing feelings for the other.  Obviously dropping the friendship entirely is a last resort.  Make sure there isn't something else you can change, first.  The main point is - be focused on them, and their marriage - not you.  You're not letting go of the friendship.  You're letting go of what you want.

The closer you are to being on their side like this, the more likely the wives will see you on their side.  However it's not something you can fake.  It has to be genuine.

I'm not sure where you are with this.  But I thought it was worth mentioning.