One day you will grow up and start asking questions. Until then we will keep telling you how much we love you, and how lucky you are to have many people that care.
But one day we will be able to tell you more.
Hopefully your dad would be able to speak to you without guilt in his heart and tell you that K and him separated because they loved you: they loved you so much that wanted to raise you in two happy, healthy, loving homes, rather than one sad and angry one. Hopefully he will explain that i came to join the family because i loved you and dad and wanted to help build a better future for all of us, including K, and of course, you. Hopefully he will be able to explain that he wanted to teach you by example the most important skill of all: how to be happy.
Until then he will just try to reassure you of everyone's love. And that's ok.