Hi,
We currently have DSS (7) with us and DH and I also have a dd who is 10 months. DSS is with us every Fri-Sun and 50% of all school holidays. DH and I are both teachers (him full time, me part time) and DSS' mum doesn't work. I think this is all relevant to what I want to say...
Dh and I had a disagreement today which is still not resolved. Basically it started around us talking about when dd re-starts at nursery for the new term. Dh wants her to go back for a day before we go back to work as he has loads of work to do (as do I) but I don't want to send her unless we're at work. So I'm trying to get it all done by spending a few hours marking once the kids are in bed. The (massive) school we work at has just held exams which is why there's so much to mark.
When I asked dh why he couldn't do what I was trying to do with my marking etc he said he was too tired in the evenings. When I suggested doing a little bit at a time at convenient points during the day he flatly refused, saying he wasn't going to do anything during the day when DSS is here, and that also goes for housework/chores etc. His opinion is that DSS doesn't get to spend every day with him so he doesn't want to waste any of that time, which I can understand.
However...I feel that there are so many things wrong with this. DSS' mum does her housework when DSS is at school or at ours. I do most of ours on my day off but there's still everyday stuff to do here which I do once dd is in bed. DSS therefore doesn't see any of the adults do any housework apart from a little bit which I do before bed. He is a very messy boy, literally undoing packaging and dropping it on the spot and spilling things on the floor and leaving it. I realise this may be totally normal for a 7yo but when he is asked to do things like scrape unwanted food into the bin or pick up his towel after it's been thrown on the floor after a bath he gets really really grumpy and starts moaning about how he shouldn't be the one to do housework. I don't think we ask him to do that much though 
Plus dh spends literally every minute with DSS meaning that both their relationships with me and dd don't really get developed that much. It literally ends up with each of us spending 100% of our time with one child and never swapping.
I also think that it's important for DSS to develop the ability to play by himself or with his sister. Both dh and DSS' mum are lovely, nurturing parents but in paying DSS so much attention, he never gets anything but 1:1 time with them.
I didn't mean for this to be so long...oops! I do think that dh is a good dad and I guess that in reading this back I've discovered I'm probably a bit jealous on dd's behalf...her days with her dad this Xmas are either spent watching him play exclusively with DSS or watching him frantically mark papers in order to get it done before DSS' arrival. Why is it ok for dd to have only a small amount of attention for long periods but not DSS for a short time?
Am I being silly about this? Any advice is welcomed :)