Here is some really good advice from one who cares.
If you and he suspects one or more of the children aren't his and you go for tests, will you tell the children? If they are not his will he love them any less? Will this news if it is bad make the children love him any less or want to go searching all over who knows where to find a dad they've never even heard of? Will this really mess up their minds? How can you not tell them if you find out for sure none of them are his! Then what? They aren't going to cancel his child support payments unless he brings this all out in the open and that will then HAVE to include the children.
Now I ask you. What have you gained besides heart ache and hurt children who are confused and now insecure and possibly scared for life emotionally?
I would opt not to have that test and just leave it up to them when they are old enough and if they ever find out the news you did. Let it be their choice. And remember this.
"The desire for money is the root of all Evil" That is what you are desiring, not to pay money or should it be said to keep your money.
You have been a wonderful Dad so far by paying your child support and you should be proud that you do and that your not a dead beat dad. You show class

.
I am a Mom with a 16 year old daughter who's father has paid 20.00 in all that time. Yup twenty dollars. Why? Because the State of Florida couldn't find him and he worked at the Florida Dept. of Transportation for many many of those years he was unfindable!
Please just know the gifts you have and be happy for the rest of your life. And just think one day you will be a grandpa!

What joy aye?
Have a peaceful night.
Brenda Lee.