In the Potterverse, the blood pact has been alternately called a Troth or an Oath, but an old fanfic that was deleted popped into my head when thinking about a phrase said in Secrets of Dumbledore: "We were closer than brothers." It is implied that even when they were enemies, Gellert only ever saw Albus as his Equal. The blood pact seems to be Old Magic, and Magic itself is very unpredictable. Would it not be too much to assume that the Magic of a Blood Pact can be varied and that the one between Albus and Gellert was more than just between ex-lovers but rather between two Husbands/Spouses? It is also implied that even after defeating him in 1945 and before, they NEVER stopped loving each other. Was it a sign of a very strict marriage, and now that it has broken, a rather demanding divorce or perhaps even annulment?