Son grows up and turns out to be infertile (because of the thing that almost killed him)
So he clones and raises his father, father.v2, as his son
The father.v2 finds out and thinks back on the love he felt, and the deep understanding for his nature that was apparent in how he was treated while growing up.
father.v2 re-clones his son, son.v2, along with his natural children, and the cycle continues; this time he doesn't die and is around to see his son grow up.
the generations communicate with a parallel set of diaries
their personalities are relatively different, and they have to adjust or tamp down some traits at certain periods of life. But every decision is informed by the infinite future and past of their relationship.
later, a son meets his father's father (his own clone) and even that guy's dad (his dad's earlier clone) - and it's amazing for them to exchange stories
through social changes the relationship adapts, and there's so much stored history and commitment that they can adapt