Just straight say it, but expect the feeling isn’t mutual.

Update my brother works with him I told my brothers wife she told my brother my brother told him that I was going to tell him I had feelings for him he told my brother he would take me with him wherever his next job takes him

I would just tell him you can’t fwb anymore and it’s because you are getting feelings for him. You totally understand if he wants to stop because you agreed to no strings and no hard feelings but you need to see other people.

Tell him and be straightforward about it. If he doesn’t want the same you have to end things. Trust me, ive been on both sides of this and it hurts if you don’t.