I read the obituary as sister of Maggie, Millie, Joyce and the late Tony and Frances (i.e. 5 siblings) all in being in UK.
i.e. Maggie - Margaret Amy born 1918 (d.1992)
Millie - Millicent Edith born 1911 (died 2002)
Joyce Amelia born 1925 (died 2014)
Tony (?) (deceased pre 1991)
Frances Ada born 1922, (d.1976)
Doris Emily did indeed have 5 siblings, and 2 were indeed deceased by 1991 - Frank Walter in 1968 and Frances Ada in 1976.
I still feel 'Tony' was a nickname for Frank Walter - I note he and wife Maude are shown as having one child on your tree (living). Have you tried tracing this person to see if FW was indeed also known as Tony?
Annette