They have been Europe's dream couple for nearly half a century and although they have had their ups and downs, breaking up has been unthinkable.
But as President Jacques Chirac and the German Chancellor, Mr Gerhard Schroder, prepare to meet in Strasbourg tomorrow, there are signs that the love affair between France and Germany is on the rocks.
Both sides deny they have fallen out and the two leaders will beam broadly and exchange warm remarks in front of the cameras tomorrow. Mr Chirac has said their biggest problem will be to find a good restaurant.
But the leaders will have to work harder to present a convincing display of harmony as they seek to reconcile conflicting views on the future shape of Europe.
When Mr Schroder called for a more integrated Europe, observers in Brussels expressed satisfaction that the German leader had finally joined the project. But the reaction from Paris was cool and French diplomats warned they would not be pressed into supporting a model of Europe designed in Berlin.
Germany wants a federal Europe, organised, like Germany itself, with a division of powers between Brussels and the member-states. Mr Schroder believes it is important to agree this new structure before the EU accepts new members for fear enlargement will produce "centrifugal forces".
As part of his reforming vision for Europe, the German Chancellor wants to redefine the relationship between Berlin and Paris, a prospect that fills the French with unease.
The political rivalry between Mr Chirac and his Socialist Prime Minister, Mr Lionel Jospin, makes it more difficult to discern the true direction of French policy. But Paris clearly favours a strengthening of co-operation among EU governments over an integrated, federal structure.
France's insistence at Nice that it should retain the same voting strength as Germany in the Council of Ministers reflects a fear that enlargement could lead to German dominance over Europe.
None of these disagreements would matter so much if personal relations between the key players were better. In the past, personal chemistry between French and German leaders often succeeded where diplomacy failed. Charles de Gaulle and Konrad Adenauer; Valery Giscard d'Estaing and Helmut Schmidt; Francois Mitterrand and Helmut Kohl all enjoyed personal friendships. Dr Kohl is one of Europe's most lachrymose politicians but the tears he shed at Mr Mitterrand's funeral expressed real personal loss.
No such warmth exists between Mr Schroder and Mr Chirac and the relationship between Hubert Vedrine and Joschka Fischer, the two Foreign Ministers, has cooled. German politicians complain there is nothing they can say about Europe that will please the French. If they call for a federal system, Paris fears France will be dissolved into an alliance dominated by the more populous Germans. If they step back from integration or say nothing, Paris complains that Berlin is losing interest.
For their part, German officials regard the French as arrogant, devious and shamelessly self-serving. Another impediment to success in Strasbourg tomorrow is that France is in no hurry to agree a common European strategy with Germany. The issue of Europe is divisive on both the left and the right of French politics and with a presidential election next year, neither Mr Chirac nor Mr Jospin will be taking any risks.
If the Franco-German relationship ceases to be the driving force of the European project, the integration project could stagnate. Despite Mr Schroder's flirtation with Tony Blair, London is not a realistic alternative partner for Berlin. Indeed, there is no alternative in sight for either France or Germany.
Like most unhappy couples, Paris and Berlin will probably just muddle through and continue repeating to anyone who asks that they are getting along just fine, thank you.