This smells fishy — like a way to protect assets from you in your upcoming divorce. Seems like it’s a perfect plan for that. You’ll never know when all that money is gifted back to your STBX.

Yes, but if you have a lot of money, it saves on taxes.

Depends. Is he getting a market wage for his work? He's probably not getting employee benefits, so you have to plus it up somehow.

Or else there's something you don't know, like that he kicked in some startup capital or something.

It doesn't seem that this was a make-work type of situation for the BIL; he must actually contribute to the company in a meaningful way that OP doesn't understand. The fact this arrangement has been going on for a decade is indication of that.

Not odd at all -- sound like the value of the contribution your brother-in-law makes (not based on hours) makes him worth it.

Depends on what deal they made.

I paid a business partner on a branch location that I needed her help starting for years after she retired because that was the deal that we had made. When she was running the branch typical net profits were $10k-$20k per month. A decade after retired I had $50k net months at that branch location.

DH has his own company. He hired his brother 10 years ago and a few years back made him a 50% profit partner. So any time he takes a distribution, he pays him a matching amount. Brother also receives a small retainer and charges uid for other various services. Brother didn’t put any money into the business and is very part time. He has other ventures.