Casement was the last of the sixteen leaders of the 1916 Rising to be executed and is quite different from the other executed men.
Casement did not take part in the Rising. He had been in Germany attempting to raise assistance for the Irish Volunteers. He returned to Ireland via submarine and arrested by British forces upon landing in County Kerry on Good Friday. Casement was subsequently tried and hanged for high treason at Pentonville Prison, London.
His widowed sister Agnes Newman was awarded an allowance of £1 per week from April 1922.

After his death, Casement became one of the most enduringly remembered figures of the 1916 leaders, due in part to two controversies that kept his name in public consciousness: the campaign to repatriate his remains to Ireland and the debate surrounding the “Black Diaries.” His connections with Ulster further heightened his prominence during the anti-partition campaigns of the late 1940s and early 1950s. In 1953, the GAA honoured his legacy by naming its Belfast stadium Casement Park. Casement’s body was returned to Ireland in 1965 (a goodwill gesture by Labour PM H Wilson).

Refs: Michael Laffan, Roger Casement, in 1916 Portraits and Lives, edited by Lawrence William White and James Quinn (2015)