Bit of background. My partner and I have an 16 month old. MIL/FIL come to our house one day a week to look after him while we go to work. My partner has a sister who i get on well with but she lives about 2 hrs away so we don't see her often, although we text regularly. This week, we were at work and got a notification on our doorbell as there was a car pulling up on our drive. My DP messaged his mum and asked who it was and she said it was his sister (SIL). We knew nothing about this visit and nothing was mentioned the day before when I was having a text convo with SIL. So when we got home, SIL had gone and MIL/FIL were quite sheepish. We questioned why SIL had been to visit yet nobody mentioned it to us. We were stood chatting in the kitchen with MIL/FIL before we went to work but no mention of it.We made it VERY clear that there is no issue with her coming to visit, infact we wholeheartedly encourage her spending time with baby. But we said it was odd that nobody had mentioned it at all to us. MIL downplayed it, said she thought we knew she was coming and just said oh well. Also to note:MIL didnt think our doorbell worked so we think they thought it would be an entirely secret visit. So, we asked again, why not tell us, and MIL reluctantly said that SIL wanted to spend time with baby when me and my partner weren't there. Reason being, because shes worried she might do something wrong etc and its easier/more comfortable for her when mummy and daddy aren't there. SIL doesnt have kids (by choice so far but has settled with her partner now so may feel differently?) and is in late 30s Thats all we got as an explanation. My partner doesnt want to push it as he doesnt want to cause upset but he is as miffed as I am about it. We just don't understand. Now, this may sound like im a control freak, but thats my (our) home and my son was in it. Me and my partner should be the ones to decide who gets to visit and spend time with our son - whether that be family, friends or strangers. The fact that it was organised behind our backs has really annoyed and confused me. And the was MIL just shrugged her shoulders like it isnt an issue made it worse. Why arrange a secret visit when she could've just said 'Oh SIL wants to pop over today to spend time with baby, thats ok isnt it...' We would have said 'ooh lovely, thats fine and left it at that. But why the secrecy? Its so odd and sneaky....and a bit weird? Any thoughts? I might sound like Im making a big deal out of nothing but things like this really get to me. Its needless sneakiness and makes me feel like discussions have been had behind our back about how we might act around people when were with our son. We are so relaxed with people though, with everything other than screen time and sugary/salty foods, so I just don't understand....