Spoilers ahead for The Society Season 1. There are a heck of a lot of life and death mysteries on The Society. Where exactly is the town of New Ham? How did the teenagers get there, and why? Will Campbell not rest until he has destroyed all semblance of peace and order? One mysterious plot line gets a little lost amid all the other drama, though: who is the father of Becca's baby? If that seems like a somewhat trivial question compared to everything else that's going on in the show, well, that's because it kind of is. Becca and Sam already decided who the father was: it's Sam, whether they had sex or not.
Becca, Sam, and viewers all know that Sam isn't the biological father of Becca's daughter, Eden. Sam is gay, Becca is straight, and the two of them have never had sex. While most everyone in town knows that Sam is gay, they nevertheless seem willing to accept that Sam is the father. As for the biological father, Becca hasn't revealed much about him at all, and seems to want to keep his identity a secret. As she tells Sam in Episode 6, "It was a mistake, OK? Nobody you know, so just leave it at that."
Does this mean that it was someone from outside of New Ham? It seems unlikely that there would be someone from their little microcosm that Sam doesn't know.
While it's possible that a potential second season could explore the story of how Becca got pregnant and with who, no one in Season 1 really seemed all that concerned with the logistics — and rightfully so. Becca and Sam decided that they'd raise the baby together, and so everyone seems to be onboard with the fact that Sam is going to be the dad, biologically or not.
When Kelly confronts Becca about her pregnancy and Becca names Sam as the father for the first time, Kelly accepts Becca's answer pretty much without question. From then on, just about everybody else does the same.
Only Grizz is upset by the idea of Sam having slept with his best friend, since he and Sam had just had sex themselves. Rather than defend himself to Grizz by saying he's not really the father because he and Becca didn't have sex, Sam holds firm on his promise to Becca, refusing to deny his role in the baby's life. It's a brave move, and to be honest, Grizz's outrage doesn't really seem so in line with his supportive, relaxed character. But then again, it does create that added bit of conflict that's necessary in a soapy teen drama.
On the other end of the spectrum, when Sam tells Gwen that he's the father of Becca's baby, she responds with a surprised but fairly nonchalant, "Huh. OK." After she turns away, she says to Madison doubtfully, "What? You know he's gay."
Madison checks her. "Sexuality is fluid, Gwen," and no one says any more about it.
It's a small moment, and from minor characters, but it does a lot to put forward the idea that if Becca and Sam decided that he's the father of the baby, then that's all there is to it. Families are created in all different ways; the mechanics of how isn't as important as the fact that they all love each other and want to stay together. And, like Sam said, a baby is hope incarnate.