The Truth is always truly there, just hidden
Severus Snape was in love with a young man, his name was Sebastian Webb. They were both passionately in love, and it was so deep that their love was able to create a baby. When Severus became pregnant, they were so thrilled. Male Pregnancy's were quiet rare but were known to happen. Homosexuality is accepted in the Wizarding world, unlike the Muggle world. Sebastian family consisted of a brother, who was older, and his parents.
Sebastian Webb was much like Severus dark brown eyes, not onyx he could hide his emotions when he wanted to. Of course he had not; he had loved Severus and he showed it every day. Although Sebastian preferred to wear dark blue instead of Black, and even James Potter who hated Severus had to admit they looked good together.
The Webb family was a known Light family, although they were not in the Order but they were light none the less.
However, their bliss was ruined, when the Webb family was targeted, the family was killed. However, the brother of Sebastian had been staying at his girlfriends that night survived when his family had not. He had sworn revenge against the Death Eaters there and then. He knew of his brother and Severus' pregnancy, and stayed close to Severus. He wanted to get to know his nephew it was the only family he had left.
Lily Evans and James Potter got pregnant at just around the same time as Severus and Sebastian. Their bliss seemed to last, however, they didn't know the horror that would end in their greedy deaths.
Nothing happened through both pregnancies, what Severus didn't know was that Dumbledore was watching the three people who were pregnant. Alice Longbottom, Lily Evans- Potter and Severus Snape of course.
However, he didn't expect them to all go into labour on the same day. The very day he was watching out for, July 31st as the seventh month dies! Dumbledore could not believe his bad luck. How was he supposed to know which one was going to be the one to defeat Voldemort?
Tragedy struck, Lily Evans- Potter's child was still born, and Severus had a son whom he called Raven Snape. Alice had an over weight boy called Neville Longbottom. However, Dumbledore could not let Severus bring up a child that may be a hero of the wizarding world.
Unregretful he obliviated Poppy, making her think that Severus' child had died shortly after being born. He charmed Severus' new born baby to take the Potter visage.
Lily and James both knew of the dark deed, for they signed adoption papers. Which were not filled out correct, because they didn't have the parents consent and a magical adoption could not be faked? Severus Snape was still alive, and they needed his consent. Dumbledore signed it as witness and sent it off.
However, that decision would come back and bite him ass one day. Nor did Lily or James realize that their greed had changed the course of the wizarding world. Just how it will change, you will need to just wait and see.