DP and I have contact with our 4 step kids Fri afternoon to Monday morning every other weekend and Monday afternoon to Tuesday morning in the summer hols. DP works 7 days a week in the summer.
Every other hol, it is at least half of the hols, sometimes more.
Why is it that when BM has a new BF she is pushing him to have the kids more? Now I have moved in, it's going to fall to me to look after them in the summer and to be honest, I feel like I've got plenty to do in dealing with them as they are. 
The eldest is 14, the youngest is 7, so DP feels they can all be left in the house with her to babysit and I can come and go as I please. This is true, but it still means I have the extra washing, all the cooking, all the general clearing up after them, and not to mention the sleep deprivation as these kids all survive on about 6 hours sleep. DP can sleep on the sofa or the moment his head hits the pillow, whether they are there or not. I can't sleep until I've had some "wind down time" after they have finally gone to sleep and then low and behold, they are up at the crack of dawn. My own DS takes 3 days to recover from the sleep deprivation as he tries his best to keep up when they are here. And I had planned on a nice day with DS having some quality time with him. Now that's blown out of the window unless I want to cart 5 kids around with me.
So when BM asks if he can have them for longer over the bank holiday weekend (when DP will be working most of it) he jumped at the chance and didn't even ask me or consider me and DS. I understand he loves having his kids around, and that's really good and should be encouraged, I know. And I feel bad for feeling like I do.
Step kids affect everyone living in the home, but it's only the birth parents whose feelings and needs get taken into consideration.
Just needed to rant about that!