Will/Testament with children and divorced

UnderMyWing🐣
Ok.... so... i am common law with my man, been together over 7 years and have 2 kids together, about to move into our 3rd house together. He was once married before.... (we never will be).... and had a child with his ex, she is now 12 years old. We are planning on writing up our Will. He says he will have everything go to me, except for his 2years worth of salary that he would give to his oldest daughter. So yes our house would be paid and car and things like that, but no definate amount of money woyld be specifically dedicated to our 2 children, yet his oldest would get about 160 000$......      i feel like that amount should be seperated between the THREE children...... our 2 kids would also get anything from me when I die, and his oldest would also get whatever her mom would give her when she dies......     
Am i wrong thinking this way? Ultimately its non of my bussiness and will let him do whatever he wants, but i feel he is being unfair.     
Thanks for your input. Just want other opinions to open my mind and see other views.