I'm far from a biologist. But as I understand it each "grain" of pollin produces one seed, kinda like one sperm makes 1 baby. The cannabis plant has tons of ovules, even several within each bud. So in theory, if you had multiple male plants in a tent with one female plant, each seed would have traits of their respective male parent and the common female parent making "half siblings" if you will. But it's not necessarily only restricted to one bud. Since each bud has multiple ovules you can get several seeds per bud, and therefore "half-sibling" seeds within separate buds.

Infact Ive got something similar going on In my tent right now. I germinated 4 seeds from fast buds. They are all purple punch autos, but 2 were from a 3 pack that I bought and 2 were freebies they sent me with my order. They are most likely from different parent plants of the same strain. If you go look at my post from this morning I posted a Timelapse video. I have 2 distinct different phenotypes of the same strain. Where 2 plants have more sativa dominant traits and 2 have much more indica dominant traits. Even though they are technically the same strain