It seems that the famed Sengoku-era lord Uesugi Kenshin never married anybody in his life because he was a devout Buddhist. This seems highly unusual, considering Japanese Buddhists at that time seem to lead lives no different than any normal person, i.e. they can freely marry and produce offsprings and even continue family lineage etc. Can his behaviors be considered extremely rare? Are there any other example of such people? Or did I get the wrong idea and actually a lot of Buddists married at that time? And is it reasonable to suppose that Uesugi Kenshin also maintained celibacy, or was his behavior only limited to refraining from formal marriage.
A lot of Buddhists got married in the Sengoku era- and in fact, quite a few daimyo were, like Kenshin, lay monks. Takeda Shingen and Otomo Sorin prior to his conversion to Christianity were two such lay monks, and they were both married and had children. And then, the leader of the Honganji sect, who was always a Buddhist monk, was also an inherited position- meaning, yes, the monks of Honganji were marrying and having children.
His lack of marriage lacks a known reason, as far as we know. There are lots of theories and rumors- ranging from, yes, that he was a "devout Buddhist" (unlikely as having a male biological heir was much more important than drinking, which Kenshin loved doing), to that he was asexual, to legends of his lack of marriage spawning from not wanting a love other than a woman he loved in his youth but could not marry for whatever reason, to very interesting rumors of Kenshin actually being a woman.
But all of those are just that- theories, and they don't really have much backing them up. So again, yeah, all we know is that Kenshin never married. We're not even sure if he was celibate, actually- just that he had no known wives or historically verifiable lovers.