Introducing person to toddler

I had a child that I placed for adoption from a prior relationship. I would love to introduce my toddler to him- he is 15 now and said he wants to meet his half sister. My daughter is now 3. This has been initiated by the 15 year old, and I support it.

My question is do I have to inform my coparent? He knows my other child exists. He never really wanted me to communicate with him, so I imagine he won't be very supportive of the two siblings meeting.

I think both children would be pissed if I kept them apart.

I think my 3 year old would also be extremely confused about who her 15 year old brother is.

Any tips? Our coparenting plan has nothing about this in it.