TMZ broke the story, Brad Pitt loaned his estranged wife $8 million to buy a house ... a little weird for an actress who has raked in millions for years.

Sources familiar with the situation tell us, Brad's income and net worth far, far exceed Angelina's ... it's not even close.

Fact is ... Angelina has not made money an issue in her divorce until several weeks ago, when she asked a judge for a formal child support agreement. As we reported, Brad has paid Angelina $1.3 million in support over the last 2 years and she didn't complain until late last month.

Our sources say Brad and Angelina don't have a prenup, which means anything they earned while they were married is a 50/50 split. That benefits Angelina, but the problem is ... they married in 2014.

Brad made more than her throughout their relationship, which began in 2004. The only way Angelina could get a cut of Brad's income from 2004 - 2014 is if she could prove they had an agreement that he would support her.

We're told she's talking about filing such a claim. But sources connected to Brad say that's laughable, because they were both extremely rich and such a promise wasn't necessary and never made.

What's super interesting ... Angelina and Brad delayed tying the knot until gay marriage became legal in California. Brad made that statement in 2006, and it took 8 more years for them to finally walk down the aisle. Had they married in 2006 she'd be entitled to millions more in community property.