Billy wasn't that lady's real son. Him living with her was a part of some social programme and it was only temporary. But, while she was good to him, she can't adopt him (maybe she can't afford it, maybe her husband is against the idea. And it was clear from the start that he's with her only for the time being).
Sherlock has been secretly very unhappy since John's wedding. But, once the child is born, Sherlock feels even sadder and lonelier, so it's probably not quite a secret for anyone any longer. I don't mind if it's not just about friendship, but Sherlock is also in love with John and is heartbroken, because John is a family man now.
When Sherlock learns about Billy's situation, he decides to adopt the boy. Why not? He's not a toddler and can pretty much take care of himself. Most people think it's a very bad idea. Because it's Sherlock. Social service workers are quite sceptical about it as well, so it's not easy (maybe Sherlock has to convince Mycroft to help him, though Mycroft, too, probably thinks it's a bad idea).
Anyway, Billy ends up moving into 221B.
I'd love Sherlock to be more like an elder brother to Billy rather than an adoptive father (I honestly can't imagine Sherlock being a father). Maybe they both have Asperger syndrome and manage to understand each other's needs better than anybody else. Maybe, because John is no longer there, Sherlock's condition has become somewhat worse. Bonus points if Billy at this point is a bit more functional aspie than Sherlock, even though they both are quite functional. If Sherlock has a meltdown, Billy knows what to do. Though Asperger thing is optional and up to you. Maybe Sherlock is just sad and pining, so Billy somewhat helps him through bad days.
Please supportive!John if we see him at all. Please, no Billy hating John. In fact, I don't mind Billy desperately trying to play a matchmaker, because he knows about Sherlock's feelings and John is very good for him. Maybe Billy doesn't understand why John can't have two families separately and make everyone happy.
Unrequited (?) John/Sherlock. Lonely Sherlock adopts Billy. Angst. Pining.
Sherlock has been secretly very unhappy since John's wedding. But, once the child is born, Sherlock feels even sadder and lonelier, so it's probably not quite a secret for anyone any longer. I don't mind if it's not just about friendship, but Sherlock is also in love with John and is heartbroken, because John is a family man now.
When Sherlock learns about Billy's situation, he decides to adopt the boy. Why not? He's not a toddler and can pretty much take care of himself. Most people think it's a very bad idea. Because it's Sherlock. Social service workers are quite sceptical about it as well, so it's not easy (maybe Sherlock has to convince Mycroft to help him, though Mycroft, too, probably thinks it's a bad idea).
Anyway, Billy ends up moving into 221B.
I'd love Sherlock to be more like an elder brother to Billy rather than an adoptive father (I honestly can't imagine Sherlock being a father). Maybe they both have Asperger syndrome and manage to understand each other's needs better than anybody else. Maybe, because John is no longer there, Sherlock's condition has become somewhat worse. Bonus points if Billy at this point is a bit more functional aspie than Sherlock, even though they both are quite functional. If Sherlock has a meltdown, Billy knows what to do. Though Asperger thing is optional and up to you. Maybe Sherlock is just sad and pining, so Billy somewhat helps him through bad days.
Please supportive!John if we see him at all. Please, no Billy hating John. In fact, I don't mind Billy desperately trying to play a matchmaker, because he knows about Sherlock's feelings and John is very good for him. Maybe Billy doesn't understand why John can't have two families separately and make everyone happy.