my father had five brothers in 1901 census one was already in the 2nd battalion lincolnshire regt they were all old enough to serve in ww1 my dad the youngest was 17 in 1914 in 1917 he was mentioned in a local paper but it said he only had two brothers serving how do i find out whether they served in the army and if they died were death certs issued for sodiers that died abroad in this country thanks

First if the brothers fought and survived WW1 go to the National Archives Web site and search the Campaign Medals of the First World War. Each brother will have his own Medal Index Card.
If any of the brothers died in WW1 You can go to the Commonwealth War Graves Commission Web Site and do a Casualty Search for them.
The information obtained from these sites will be a starting point for furthur research into your fathers brothers.