I've posted this is step parents but I'm being brave and posting here too for a balanced view.
Basically DP's kids live with their mother. Mine live with us.
A few weeks ago it was DSS's birthday and we threw him a party, had his girlfriend over, bought him a cake, gave him £50 and a bottle of vodka. He then went home and had a party dinner with his mum and her side of the family.
Now my DS's birthday is in feb. I've always given them £100 each however DP is saying that this year they'll only be getting £50 as that's what his DS got. My argument is that his DS would have had a lot spent on him from his mother, his main carer. I'm DS's main carer, whilst he'll get about £20 off his dad that's not the same as what his ds would have got from his mother.
AIBU to want to stick with giving my ds's £100 each? They live here, we get money for them in the form of child maintenance etc as does his ex from us for their kids.