Do your step children get treated like guests?

[Teasynurse]

DP just came home from work to get changed before going to collect DSS (15). While he was here, he put the hoover round and made sure DSS's room was tidy. He asked what we were having for tea; bangers, mash and beans (I've had a hard week and can't be arsed faffing tonight) he suggested maybe we could have something nicer as DSS is coming.
DSS comes to stay twice a week. DP has to drive 40 mins each way to collect him and take him back. We live quite near a station and the train would take 10 mins per journey but he doesn't like using public transport so DP or I have to drive him.
He doesn't speak to me or DD (16) unless it's to answer direct questions and while he's here he sits in his room playing Xbox. Also, before now I have spent ages cooking tea only for DSS to wolf it down in silence before sloping off back to his room before the rest of us have finished and DP expects my DD to clean up (I told him he could help me!).
Am I being unreasonable to have a word with DP about this as it's starting to get me down.

My OHs son comes and stops with us on weekends, and comes for dinner in the week occasionally too. He’s 10. Me and OH have been together since he was about 15m old.
We have a good relationship, and I treat him no different to mine and OHs two girls. I do nothing ‘special’ for him as such; he likes Shephards Pie so I’ll wait til the weekend to cook it, but if for any reason he didn’t come over I’d still have cooked it. I’ll ask him (at the same time as the girls) whether he’s hungry, and like the girls, he brings his clothes down for washing and is expected to tidy up after himself.
He has his own bedroom, his own TV, Xbox, tablet etc and like your situation, when he comes round he just likes to chill in his room and generally ignore us unless he wants something!
I think with being 15, wanting his own space and time alone is normal.
The way your OH is acting however I wouldn’t consider normal. If my OH asked me to do a special meal or to get the girls to tidy just for his arrival I’d be miffed. I’d also ask ‘since when has he become royalty’ but that’s just me as I’m a bit of a sarcastic cow haha.
I’d personally skip your OH, and ask his son directly ‘what do you fancy for dinner’. If he’s tucked away in his room, knock the door first and say ‘is it okay for me to pop in a sec’ rather than just barging in. Small convos like that will all add up and may also show your OH that he can be treated the same as any other family member.