First a quick clarification...Your brother-in-law may be the agent-in-fact for your mother under a power of attorney (POA) arrangement, or be the current trustee of your parent's trust, or both. But one cannot be POA for a trust.
A POA arrangement would be for looking after any of your mother's business affairs that aren't included in the trust. Technically, it would be inappropriate for your brother-in-law to share the details of that with you unless your mother asked him to. He owes your mother a duty of privacy in those matters.
Similarly, since your mother is still alive and, presumably, benefitting from your parents' trust, if your brother is serving as trustee then he has a duty of loyalty and privacy to your mother regarding trust affairs as well.
When your mother passes, if you are one of the trust's beneficiaries and your brother-in-law is the trustee, then it's a different story. As a (then) beneficiary, you will be entitled to know the appropriate details of the trust and how you will benefit.
Treat this as general information to help provide some context for you. There may be additional details or nuances not included in your question. Please consult a qualified estate attorney for specific advice on your standing in this.
I hope that helps and that you're able to sort it all out to the satisfaction of everyone involved.