I got married several years ago but only sought permission of my stepfather (mother's husband) because my biological father has removed himself from my life since childhood. He now knows about my marriage and has no objection. Is my marriage valid?
Yes, your marriage is valid.
Your stepfather has no say in your marriage. If you were virgin (first marriage) you needed permission of your biological father if he has not removed himself from your life.
Even after marriage, if your biological father who looks after you agrees, the marriage is valid. In any way, according to what you have written, your marriage is valid.
Wassalam.
Mohammad Al-Musawi