It was in one of the small magazines like Asimov I think in the late 70's or early 80's. In it, there were just lines of clones, and mating occurred between "fathers" (elder clones) and "sons" (younger clones) (yeah, ick) on "Pool Day." But this one son wanted to mate with another younger clone rather than his elder clone. It was really weird, but stuck with me. Any help finding it would be appreciated.
Rand B. Lee's "Full Fathom Five My Father Lies". IASFM February 1981. I still have the magazine.
A review from librarything: "Full Fathom Five My Father Lies by Rand B. Lee is an amazingly original take on cloning and a future society. It centers around a lost human colony, where only the men survived and must perpetuate by use of a special cloning pool. They have lost most of their history and understanding of their technology. They have forgotten that there was ever anything other than "Fathers" and their society has grown to dictate that only "Fathers" and their "sons" (their clones) must be lovers. But what happens when one Father's clone falls in love with someone else? "