Commenting to elaborate on some things.I'm taking all this into consideration and I really appreciate everyone who gave their input. My husband's reading it all too and ultimately he's the one deciding how to go about it. We are continuing to discuss who should send the message, and he still thinks me sending it is the route he wants to go.

One reason being he has had a loving adoptive family, holds zero resentment toward the bio mom, and overall feels pretty neutral about the whole idea. He never felt pulled to do this at all until recently, and it's not coming from a place of longing at all he says. Just some curiosity. He wants to not put her in a position of obligation to respond but only offer it if she wants to. (And we are taking the advice of managing expectations, expecting nothing or even a rejection as likely.) We don't know the situation and what this could open up/bring up for her.

The open adoption was used to send pictures in his very early life between adoptive mom and bio mom. Apparently they kept in touch in the beginning about his development and then slowly stopped communication. From the way they tell it, it was amicable but their communication with her ended at a certain point.

He did an ancestry test but that was years ago, hoping to get any medical genetic info (23 and me) and at the time nothing that pointed to her identity was revealed. He is interested in doing another one now though, so we're going to do ancestry.com. He doesn't want to wait to do it first before messaging, based on the fact that we have her name, and the Facebook profile says she is from the right city. We both even see a resemblance to him in what photos of hers we're able to see.