Just because the OP earns less than her husband, doens't mean she is worth less and I think it's a little bit harsh to say she is unwilling to provide for her own children as much as her new husband is! It's not about money. She will be at home more often than her H, she is making a home for him, she is bringing up his children (and it sounds like he regards his step children as his children as they are a family and he is the only father figure they have)
Everyone's personal circumstances vary and people's ideas of what is right do, but it doesn't necessary make them right or wrong.
I don't think there is anything wrong with having the money go into a family pot when one person earns less than the other. It can work if you can make it work .... but at the moment, Op, it isn't working.
I agree with you totally that waiting until you are working full time and earning more, so can afford to set up saving accounts for your own children is a good idea.
Can you really do a budget where you allocate exactly how much is spent on every child? I'd love to know how it works, and I'm not making a dig, it's a genuine query.
The bottom line is when the step children are in the house, they do not necessarily have to have equal money spent on them as the children living in the house because a) the step children have their mother and her family providing for them as well, she is receiving tax credits (possibly) and child benefit for them and b)their father is paying maintenance for them which is supposed to go towards a lot of their needs.
I appreciate it is very difficult to explain to a child though, as with the toothbrush incident.
I think you should do what you can afford, trying to ensure no children are left out and factoring in your H already contributes to his biological children with his maintenance.
But really, what the hell do I know? It's only my thoughts lol