This was mooted before but went nowhere. SDLP have been in the wilderness for a long time and show little chance of resurgence; FF want to be an all-island party. Makes some sense, I suppose.
But are they aligned on policy? They are talking about the European elections but they sit in different groups in the European Parliament. SDLP is in the Progressive Alliance of Socialists and Democrats (S&D) while FF is in the Alliance of Liberals & Democrats for Europe (ALDE). (FG is in the European People’s Party)
Maybe FF could try to move group but their membership application could be blocked by existing S&D members - which include the Irish Labour Party. Labour must be feeling a bit aggrieved that their supposed brothers in the SDLP are getting into bed with FF. I’d have thought that Labour + SDLP + Social Democrats might have been a more coherent group but none of them have a certain future at present so I suppose hitching to the FF machine is a pragmatic move.