Michael Gallagher said he did not set out to start campaigning and described the toll it has taken on him and his family.
The Omagh Bombing Inquiry is examining whether the 1998 atrocity could reasonably have been prevented by UK authorities.
The Oasis frontman is believed to be building a large pool in his back garden, despite admittedly not being a good swimmer.
Liam Gallagher is building a pool in his North London mansion, despite previously sharing that he "can't swim".