How do I sneak back in at night?

So, I see a lot of questions about tips for sneaking out, but I'm more wondering how to sneak back in? I usually leave the house in the evening and tell my parents I'm staying over at a friend's house, and then meet up with my boyfriend. I can't sleep over at his house because neither of our parents allows it, so I usually get home around 2:00 a.m. It's hard to go to a friend's house then either, because knocking on a door at 2:00 a.m. usually wouldn't be okay with my parents, right?

Then I usually go home but now I have the problem that since my brother lost his keys we only have a few. On top of that my parents always lock ALL the doors at night (so I can't take them with me). I can climb over the front gate OK, but how do I get back in? I was thinking of opening a window to the kitchen and then climbing through. There is a risk that my parents will close it, but they never actually go into the kitchen at night. My biggest problem will probably be the neighbors because every time we move the light comes on. I don't want them to think there's a break-in and then the police will come. Any ideas?