I personally think it'd be more likely that his love was expressed in his creating of them. Love doesn't always equal six. And he did have an affair with Almalexia. She got around.
That'd make a great trivia question: "Almalexia was a massive [censored]. Who didn't she sleep with?" Now all we need is an answer.
Daedra are definitely capable of six, lesser and greater ones. They are also capable of love (Battlespire). Procreation? Maybe not in the way we understand it, but I wouldn't see it as impossible. I mean, let's try looking at it this way:
Vivec and Molag Bal bang. New beings are produced, these are
divine monsters. In TES Divine beings are ideas and forces personified, like time, nature, debauchery, destruction, madness, fate, etc. Therefore the children of Vivec and Molag Bal are evil thoughts Vivec thought as he was being violated, and the divine union gave them form. He then had to both literally and symbolically take control over his rage-induced (and therefore destructive) desires.
and that is why literature is awesome.