Yes you have the right to demand for DNA test since there is an established fact that you had something together coupled with the fact that the baby looks like you.
Haba
Get a lawyer to write the family officially informing them about the situation at hand and the need for DNA test to be conducted to reveal the truth.
If they refuse to honour the request
The lawyer can proceed to file a suit in that regard so the c0urt can come into the matter and give instruction that DNA should be conducted.
Once DNA reveals the child belongs to you.
The husband has the right to demand for everything he has spent on the child, those are payments he has evidence for only and you will have to pay them before you get access to the child.
If the child is still below 15
The mother may retain custody while you get access to visit and have the child visit you from time to time.
But the husband will know clearly now that he is not the father of the child.
And in the situation here the DNA result comes out negative that you are not the owner of the child.
You have nothing to fear cos the case was based on established fact not just assumptions and the c0urt is the one who handled the whole thing.
And no case of wrong accusation here or false claim so far you did not confront the family yourself
If they did not tell anyone
No one will hear about it
Ignorance of the law is no excuse