My husband found out last week that he might have a son that's 16 that he never knew nothing about. I need to find out what legal stauses we have. Can she file child support even though he didn't even know about him? And can she file back child support? What rights does he have even if he is named after another guy? And there is a possibility of more than one father?

Yes, can file for support. Unless a support order was entered in abstentia then there is no "back support" but I'm not sure if Tx allows retroactive support, but generally it isn't allowed.

There can only be ONE father. However, if the child has a legal father, it may be too late to change.

Basically, he needs to see what the child and mother want. If they want anything from him then he should first demand a paternity test. Then you go from there.

Agreed, if he is indeed the father, they can file for child support. Unless they filed for support in years past without your knowledge they should be no back support.

There also can not be two legal fathers, merely having a name is not the issue, but if a father is on the birth certificate

... and there is a possibility of more than one father?

As I recall my high school biology, that's not at all likely.