I came to therapy very late in life and it was similarly opaque to me. I was very fortunate to come across someone who listened to me talk about my life and distilled it into insights I had never made on my own. I can only assume they've seen so much and treated so many patients they have a deep well of patterns to start with and it's mostly of matter of seeing where you fit plus whatever is unique to you.

I've always had a good relationship with my mother but it was only though my therapist I even realized I did in fact have some attachment issues. Anecdotally when I mentioned that to my aunts they immediately starting sharing stories about mom. Family knew all along but they remained silent until I asked for detail. The point is for both the therapist and family just talking is enough to prime the process of discovery. You won't start with a giant epiphany.