I’ve been a stepdad (44) to my stepdaughter (12) and stepson (10) for the past 8 years. They live with us half the time. SInce they moved in 6 1/2 years ago I’ve paid half the rent, half of utilities, and half of groceries with my SO. In a way, my expenses are much more significant than when i was alone, but i see it as teamwork. she also pays half the rent, half the bills and food and also gave birth to my son, which we split all related costs on together. She also came with everything we needed for a baby boy, ages 0 to 6 (clothing, toys, etc.) so honestly, I’m actually saving thousands of $$$ and countless hours pf shopping. There are no perfect formulas, only the ones that work best for both of you. My step kids i see as being like my own, every penny spent is a moment invested. Live life with love.