The hires come after former Sunday Express editor Douglas, aided by ITV’s former managing director of brand and commercial, Howell, launched a failed bid to buy a majority stake in the group’s Sunday People.
Sunday Brands, the new subsidiary, will include The Sunday People, The Sunday Mail in Scotland, Wales on Sunday and regional titles the Sunday Mercury in Birmingham and Sunday Sun in Newcastle.
Trinity’s biggest national title, Sunday Mirror, will sit outside the division, closely paired as it is with the Daily Mirror under the one editor, Lloyd Embley.
In addition, Howell will act as group transformation director, reporting to the chief executive. He will work with the team on implementing and accelerating the company’s strategic transformation plan.
Simon Fox, chief executive of Trinity Mirror, said: "We have got to know Sue and Rupert well over the last few months and are really delighted that they have agreed to join us. Ours is a talent and content business, so to attract talent of this calibre is a real coup."
Douglas said: "I've spent the last two years pursuing a dream to revitalise this part of the media market, so I'm thrilled to get the opportunity to lead the re-vamp of the Sunday People under James Scott’s editorship, as well as develop the other Sunday titles.
"This is a chance to put energy, fun and great journalism into what will become a seven-day digital, one-day print operation."