I doubt Mike And Andy had access to Morrissey and Marr's bank records...so it's reasonable to believe they thought they were getting the same amount they were getting....
You don't need to see your partner's bank records. Get a lawyer and get an audit. If you're taking the position that they didn't know, I'm taking the position that they should have tried to find out. What I'd always thought is that they didn't know because they were partying and enjoying being rock stars while the business matters were being handled for them. If that was the case they couldn't really complain.
But on the other hand, it seems they did know, found it unfair, but agreed to it. If that was the case they really can't complain. This is actually a better case for Morrissey/Marr, makes them look like honest businessmen, whereas the first scenario makes them look like everyone else in the music business.
I've read about the Rolling Stones, and they're sort of notorious for crediting songs to Jagger/Richards even though the songs were "written" as jams with several people contributing. Ron Wood said in an interview "for several years I was credited 'inspiration by' ". Did he pack it up? No, because he was in the Rolling Stones. That's how it works.
Then you have Van Halen that divided everything 25% each member. So even though Michael Anthony never wrote anything ( I think), and a lot of times, it's Eddie playing bass on the records, he still got 25%. For them, that's how they did it. Now in their case it meant that Eddie was getting his brother a good deal, since he was the drummer and wouldn't have gotten writing credit in most situations. I guess a lot of the biggest hits, the early stuff, was written byt Eddie and Alex jamming, making demos, and then David Lee Roth taking the tapes and putting words to it, so whatever. I'm just saying there are different models.
The Beatles are interesting. George had to write his own songs by himself and would be lucky to get two on a record. Wouldn't it seem that with their "all you need is love" mentality that at some point, George and John might have written a song? No, it wasn't allowed.
People do it different ways but a contract is a contract. If you pay me to mow your lawn, I can't come back the next day and ask for more money for work I already did.
It's nice that you are for fairness, but I just think a contract should be honored. Yes, renegotiation is allowed, but once the work is completed? No.
Also, I always think, if The Smiths were offered a reunion tour and Morrissey and Marr decided to do it, what percentage would Mike Joyce work for? He wouldn't walk away from 10%. That's the bottom line.
If I had my way, Morrissey would demonstrate this by doing a Smiths concert with Joyce, if he would sign a new contract giving up all past claims, and agreeing to get 10% of the proceeds of maybe a London/Los Angeles "Pink Floyd The Wall" type of "tour". Everyone would benefit and it would all be over. I'd also start the negotiations offering 5% in case he'd settle for 7%. Give the extra 3% to PETA and get the tax deduction.