Does that matter to you? Would it change anything? If they are already grown, chances are you already love those kids to death and would do anything for them. Would you walk away if turns out they aren't yours and never contact them again?

If I was a man - yes, obviously for me as a mother it is not an issue.
Reason 1 Piece of mind. I would rather know the truth than live in suspense and let my imagination run wild. It has to do not with the child but rather with having solid proof of possible infidelity. To me clarity brings closure.
When someone has a child from another man and lie about it they take away their choice. This idea is really tough to live with even if you love the child bio or not bio.

Reason 2 genetic illnesses. I think it makes a difference for a clinician attempting to diagnose and/or treat certain conditions to know if there is a question mark in the family tree.

If I were a man, it wouldn't matter to me if they were biologically my kids or not. I raised them, I nurtured them, I love them no matter whose sperm helped create them, they are my kids. If the kids wanted to know, I would have it done for them.

I would want to know, for similar reasons as Aronia, plus if you are not the boo dad, I'd wonder if the bio dad might step forward at some point.

About how old are your kids (adults)? If they are older like that, it would be more difficult to test, without them suspecting something if you kwim. What would you tell them prior to the test (why they are being tested)? Do you have good reason to suspect you are not bio dad?

sorry that should say bio not boo dad, on my phone....

I would want to know, but I don't think it would change my feelings for my kids.