Leo Jones was the son of Francine Jones and Clive Jones, the brother of Tish Jones and Martha Jones, the father of Keisha Jones by his girlfriend Shonara, and the cousin of Adeola Oshodi.
When Leo Jones celebrated his 21st birthday, the party ended in a fight when his father's girlfriend Annalise claimed that Martha's trip to the Moon never actually happened. (DW: Smith and Jones)
Leo witnessed Richard Lazarus turn 40 years younger and witnessed the havoc that Lazarus created. During this occassion he met the Doctor. (DW: The Lazarus Experiment)
Leo was in Brighton with his girlfriend and daughter when The Master had his parents and sister arrested so he avoided capture after Martha warned him. (DW: The Sound of Drums)
It is unknown what happened to him during the following "Year That Never Was" and no mention is made of him in ths period. However, once time has reverted to its correct point, Leo is seen with the rest of the Jones family, but appears to be the only one with no memory of the Toglafane invasion and the Master's reign.