Seeking Guidance for My Brother’s Relationship

Assalamu alaykum. I need advice regarding my brother. We were raised in a mostly secular Muslim environment, where people identify as Muslim but don’t practice much. After moving to Canada, I (his sister) began studying Islam seriously, took my shahada with conviction, and started observing the deen. At that time, I was in a long-term relationship with a non-Muslim man, and we were planning to marry. We parted ways because he couldn’t accept Islam, and I could not continue with a non-Muslim spouse. As for my brother, he hasn’t made a formal reversion, but I notice him drawing closer to Islam, eager to learn and begin praying. He’s involved with a young woman from a similar secular Muslim background. She told him she was Muslim, they kept things halal, and they intended to have a nikah soon. Recently, though, he discovered she isn’t truly a believer-she was pushed to practice as a child and has only basic knowledge. She even voices concerns like women being compelled in Islam and debates evolution. My brother is torn and asked for my counsel. I worry about giving wrong advice because he trusts me deeply, especially since I’ve been in a comparable spot. He’s upset she hid this, as he envisioned marrying a Muslim woman to build a family rooted in Islamic values. If they do a nikah, would it be void? Should he end things? For now, I suggested he deepen his own Islamic knowledge, research, and perhaps share with her gently. He doesn’t want to force her-guidance is from Allah alone. My brother is 26, and she’s 22 or 23. She’s quite young, and her views might shift over time; I was very different at that age. She’s truly a wonderful person: intelligent, hardworking, kind-hearted. So I hesitate to tell him to break up right away, especially since finding a suitable spouse is already challenging. May Allah grant clarity.