The prime minister’s brother, Jo Johnson, has warned against a proposal to cut university tuition fees. The younger, Remain-supporting Johnson – who was universities minister until September when he resigned from government citing an “unresolvable tension” between his family loyalty and the national interest – argued that lowering student fees would do “grave damage” to higher education finances. The former Tory MP, who stepped down at the election and is now chairman of the group that owns the Times Educational…