Worried about our neighbor kid

We live in a really nice, safe neighborhood. Double townhouses throughout. Our direct neighbor who we share a wall with has a young son. He’s 12 years old and a really polite, sweet kid- I’ll call him C. I have 4 kids. My oldest is a girl who’s 11 and then a 9 year old son who attend the same school as our neighbor and ride the same bus. C lives with his single Dad. C comes home to an empty house after school every day- which is ok, he’s old enough and mature enough. But the problem is the way him and his father go about this. His Dad will leave their garage door open for C to get inside. But the Dad is constantly forgetting to leave the garage door open. C knocks on my door to use the phone to call his dad regularly. Then his Dad will open the garage door from wherever he’s at. I’m guessing it’s an app or something linked to their door. Well I’ll invite him in every time and make him a snack and ask about his day. Real sweet boy. Then he’ll play with my kids until he gets ahold of his Dad and gets let inside his house. Yesterday I had picked the kids up from school and we went out to run errands and eat out for supper. We got home around 7pm, pull into our driveway and I see C on his front porch. It’s dark out and his sitting on the porch step, leaning over and resting on his book bag. My heart sank and I was furious. I hugged him and brought him inside, made him something to eat and he called his Dad. I was expecting to hear his Dad apologizing profusely and saying he’s rushing home. Nope. C was on the phone for 2 minutes and hung up, then we heard their garage door opening. I asked him when his Dad was getting home and he shrugged his shoulders. The thought of this poor kid sitting on his front porch from 3-7 and then going to an empty house and putting himself to sleep- not happening. I told him to call his Dad back and tell him that he’s staying the night at my house. I gave him some pjs and washed his school uniform so it would be clean for tomorrow. My kids had a sleepover on a school night and were thrilled. They all are off to school the next morning - and it gets worse. I hear from my two oldest kids that C told them that he’s had sex before! He’s 12. I thought he was just telling stories, tryna be cool. Well, it didn’t set well with me. None of this sits well with me. The very next time I see C, I straight up tell him what my kids said and ask if it’s true. He tells me yes. I ask a hundred questions. It was with a 14 year old girl. We have a super long talk. I tell him everything that I would be telling my kids in this situation. He begs me not to tell his Dad, pleads for me not too. I’m completely divided about how to handle this. Part of me wants to go off on his Dad and tell him what a shitty job he’s doing in all aspects of parenting. And part of me wants to just continue taking care of C whenever he needs it and be that adult he can go too. My husband doesn’t care how I handle this, C just isn’t allowed to hang out alone with our oldest daughter anymore. What would y’all do? via /r/Parenting http://bit.ly/2wvDJRq