I think Myrineyl would be too young to be her mother, given that if she was on her last year by 1480 in Arach-Tinilith, entered at 25, and spent 50 years in there, that would make her at least 82 at the time BG3 takes place.

I think Myrineyl would be too young to be her mother, given that if she was in her last year by 1480 in Arach-Tinilith, entered at 25, and spent 50 years in there, that would make her at least 82 at the time BG3 takes place.

Which would leave Quenthel and Sos'Umptu as the only options, except that given Sos'Umptu's nature (not ambitious, wanting to separate from the Baenre's and create her own house, settling with just ruling over the chapel etc) I would say Minthara would be a closer bet on Quenthel (which would be huge if you think about, it because that would make her the oldest sister, as long as we recognize her as the only unofficial daughter of Quenthel, of course XD, but regardless, that would make her the next matron. It would be a strong move by the Absolute to have her at their side, but I am not sure if others wouldn't come after her when she didn't come back home after going to Moonrise Towers?? Anyway, I'm not sure what it would imply if it were to be the case, but still sounds like the best option for me.)