The couple first met on the set of Pushing Tin in 1999 and were married the year later after is Las Vegan only two months of dating. They didn't get together right away as Thornton was still engaged to actress Laura Dern and Jolie was supposedly dating actor Timothy Hutton.
The pair were most noted for their 20 year age difference and their strange displays of affection, namely wearing vials of each other's blood around their necks. Thornton defended these 'acts of love', confirming that they were in fact lockets with only a single drop of each other's blood in them.
When they were first married the pair moved into the Beverly Hills home that was previously owned by Guns N' Roses guitarist Slash.
The couple adopted a child, Maddox, from Cambodia in March 2002, however it was later found out that Jolie had adopted the baby boy as a single parent while she was filming Beyond Borders.
They eventually separated in June 2002 and divorced in 2003. Jolie famously made reference to how little the couple had in common and the importance of getting to know yourself before getting married in reference to the breakdown of the relationship. She said; "It took me by surprise, because overnight, we totally changed. I think one day we had just nothing in common. And it's scary but... I think it can happen when you get involved and you don't know yourself yet. (Wikipedia)
'I'm angry. I'm sad. It's a very difficult and sad time. It was a real deep connection, a deep marriage, so it's not that simple to say this or that one thing caused the problems. It's clear to me that our priorities shifted overnight. He's focused on his music and career. I'm focused on my baby. It comes down to what's important to you.' (IMDB)
Jolie did have a Billy Bob Thornton tattoo, however has since had this covered over with the coordinates of the birth countries of her children, with France featuring twice for Knox and Viv.
Source IMDB and Wikipedia.