Many of you will be unsurprised to hear I am not coping very well with having DSD(14) living with us. In some ways she is very easy partly because she is out all day (when I'm at work) and then either follows DS around or sits in her room alone. She is not really getting involved in "family" life at all. She's certainly not "hassling" me. She's not talking about her feelings or emotions to anyone at home.
DS normally loves the opportunity to play board games, but because DSD "poo poo-ed" it, DS does too now. We would normally have 1 night a fortnight when DP goes out to ourselves to watch a film at home or do other things together. We would be out in the garden most evenings, kicking a ball around or him helping with gardening for 20 mins etc. All that has gone now because DSD is following him about and making fun of him for doing all that stuff. Of course, when he is entrenched in a computer game, she goes to her room and leaves him alone. I'm finding more and more that DS is grumpy and just wants to sit on a computer. 
I always used to "write off" DSC weekends with DS and let him just get on with DSC, but now we have DSD living with us, I can't "write off" spending any quality time with DS at all, or live my life hoping DSD will go out for the evening.
I find myself creeping around in the mornings, trying not to wake DSD so I can get 5 mins before work with DS alone. 
I've had a few days "holiday" with DS visiting our family, and it was so nice and DS and I were "ourselves" without having to worry about everyone else. Funnily enough he didn't miss his computer games at all and interacted with everyone really well.
DP, of course, is not helping by allowing DSD to stay out all week (when I'm at work and DS is therefore home alone) and then insisting DSD stay home at weekends and evenings! I had a moan and he apologised, but I doubt anything will change.
And then there is DP behaviour. Him coming in from work and running upstairs to see DSD whilst simultaneously ignoring or semi ignoring DS. Him spending a minimum of 40 mins driving DSD around everyday (despite him telling me this wouldn't happen and if DSD wanted to live with us, she would have to get lifts / bike / or not go out everyday) whilst telling DS to take a bike or that he has to wait for me to come home from work to pick him up.
She is also, of course, getting masses of DP and I time in the form of us discussing her mental state, her Mum being in contact and us "deciding" on what contact she should have with her Mum, maternal family etc. Everyone we talk to feels sorry for her and although I do too and am worried for her state of mind, I am finding I am begruding spending so much emotional energy on her, and then of course, there's the impending court case for contact with other kids, the never ending bitterness from the ex wife, bad behaviour from other DSC and all the other stuff that goes on.
I do try and involve DSD and am treating her the same "on the surface" but obviously I am resentful that this young lady is getting sooo much attention whilst DS is getting even less of my time.
So, do you find your relaxed home life changes when DSC arrive, or is it just me being uptight or because DP is not supporting me in my need to spend quality time with DS?