If you have previously recommended this thread, you should see a tick / check mark on the recommend button. Click the tick to undo the recommendation (the tick may appear to change to a cross as you do this.) If you added a comment with your recommendation, you will need to delete that from your facebook wall separately.
if it is important for you as a family that the dcs go and choose presents for their parents (including you as step parent) then you as a family (you and dh) need to enable dss to do this by offering (before xmas eve!) to take him shopping to get his xmas presents. even if it is just for his dad and brother. you cannot expect his mum to be buying gifts for you/his dad and your child!
As a single mum I would give ds the money and send him into a shop and buy me a present as I had no one else to teach him to do this. I also taught him to buy his dad a small gift.
As a step parent I have always encouraged my step children to buy for their dad but now they're teenagers, I remind them once but refuse to nag.
Dp does the same with ds for me.
In your case, I would stop getting annoyed with dss mum even if she is rude and not teaching dss the right lessons. I would start encouraging and helping dss yourself with the help of your dp if he sulks and moans. He needs to learn that life is about give and take and that you and dad are not just wallets but real people with real feelings.
I've always assumed that it is my job as SM to help my DSC buy their Dad a gift/card for Xmas & birthdays.
DP takes my DD to buy me a gift and I do the same with DSS. I make sure my DD buys DP and DSS a gift.
DP does check that DSS has bought his Mum something and helps him make a cake or similar for Mother's Day - but that's because there isn't anyone else to do that with him - we do it for DSS, not for his Mum!
Agree his mums at fault on this one, either your DH needs to make sure he gets brother a present and you but not his mum, or his mum does it for your family ad you do it for hers.
Fwiw my DSS is 14 and we've taken him for his mums presents, and card, she does the same for us,I even ad chocs on Mother's Day this year which made me cry, as it was from both of them appreciating what I do for DSS. To be fair DSS mum is pretty fab though.
If your DH regularly helps his DS buy a present for his mum, it would be nice of her to recipicate. But if she doesn't I think you probably are expecting a bit much of an 11 year old boy to go out and buy his dad or brother a present from his own resources. Why don't you take him out and help him? DP did that with my DCs for my birthday recently - just took DS with him on the supermarket run and chose some chocolates and flowers for me, and I really appreciated it