Favoritism between grand children

My ex has a daughter with someone else and I have two boys will him his daughter and my oldest son are 4 months apart in age and both highly active. His mother always has his daughter every weekend most everyday but never wants my boys back in April of 2021 she threw a big party for his daughter’s birthday and had a buffet of food all the family and I even went with my sons but when my boys birthdays rolled around she got one a to small pair of shoes and the other a toy boat for the tub. It irritates me so much because the other bm is just so irresponsible and uses the time to shake a$$ in the bar and I need the help to work! I took care of her son while he was in jail for a whole year and had to quit many jobs because his mother offers empty promises to help and doesn’t. I’m tired of my boys being second best or least favorite what do I do? I’m in no way saying she’s obligated to help it just feels wrong.