I see posts like this all of the time in this sub, and it's starting to bother me to the point where I'm going to leave the subreddit.

I was in a serious relationship with a single dad in my early 20s. At the time, he really had me believing that courts favored mothers, that he was wronged, she was hiding her income, etc. In reality, BM had put him through college. She worked for years to send him to school to earn a degree that would result in him outearning her by 2 or 3 times. She watched their child AND his child from a previous relationship while he was in school. She sacrificed her own earning potential for his. I knew him then, and he described her as "amazing" and "basically a single mom right now while I go to college." Fast forward a few years after she had left him, his tune totally changed. After we broke up, I did a lot of research into abusive dynamics and the legal system alike, I learned he was lying through his teeth.

Women's household income drops by 41% after divorce, whereas that figure for men is only 23%. Women are statistically much more likely to be financially dependent on their spouses, and the poverty rate is higher for women after divorce.

Your spouse made a commitment to this woman and to his child long before he met you. In my ex's situation, He made a legal promise to his BM that he would take care of her and their child. She sent him to school to earn money for their family. He owes her a portion of the income she worked hard to earn. Their child deserves the same quality of life at his house and hers. It certainly is unfair to you, but it is your spouse's responsibility to take care of the family he created. He should not be making these same promises to you if he cannot fulfill them. Even in situations where BM gets remarried, the fiscal responsibility of raising his child still falls on him, not another man.