Re: Blended family
I'm on the other side of that equation, my GF has a son from a previous marriage, the 3 of us live together. My children are grown but I still support my younger daughter to some extent.
We split everything such as vacations, food, utilities, so I'm essentially paying half of his day to day living expenses and that sort of thing.
Things he needs for himself (clothes, sporting equipment, hobbies, spending money, camp, extrcurricular activities, school lunch money, etc), that's on her. She gets some help from her almost broke exhusband who pays for his phone and some of the items he wants or needs. Sometimes I'll get him something he needs. Not often, but sometimes.
Hope this helps.