I had kuhli loaches breed once for me, unknowningly.
I bought 5, all made it fine, had them 2 years or so.
When I was moving fish around, I could only catch 4 of them. I got tired of trying to catch the last one and decided to leave it on its own in the tank. I was breeding Badis badis and didn't want either species harmed by the loach being in there which is why I was wanting to move them out.
About a year later, I found 7 in the tank when I broke it down. The other tank still had only 4, so I can only presume they had bred when all together and when I caught the 4 originally to move. It was a heavily planted tank, and I never saw more than one when trying to catch what I presumed was the last one in the tank. Perhaps the other 6 were really small and I just never saw them. By the time I got the 7 out, they were all pretty much the same adult size.
Fish do their own thing sometimes, when left to their own devices!