A lawmaker is proposing guidelines to address the complicated question of when a parent is a parent and when a parent isn't.

For example, if a divorced man finds out 10 years later he is not the biological father of the children born during his marriage, does he have to pay child support?

In contrast, if that same man discovers those children weren't fathered by him, does he have a legal right to visitation?

Guidelines to these and many other paternity issues are found in Sen. Lyle Hillyard's Uniform Parentage Act, discussed Wednesday during an interim meeting of legislators.

While the Senate approved the measure during the general session of the Legislature earlier this year, it never made it off the boards in the House, which in effect sent the bill back for committee review. A decision isn't expected until November.

Hillyard, R-Logan, concedes the House's inaction was due to the bill's complicated nature.

"This is at the top of the list of the most important issues we will deal with," said Sen. Chris Buttars, R-West Jordan. "We're talking about the constitution and makeup of family."

The major components of SB45 address the parameters of challenging paternity through DNA testing — an issue that can accompany child-support disputes — and gestational surrogacy agreements, which are non-binding under Utah's current law.

Paternity challenges and the flood of questions that follow have made collection of child support in these cases a complex nightmare for the Office of Recovery Services, said executive director Emma Chacon.

"We deal with this issue day in and day out. "What we are looking for is some guidance . . . guidance that is sorely needed now."

Utah "presumes" the husband is the biological father of any children who result from his marriage to the wife who becomes pregnant.

But in bitter breakups, a wife might confess that children born years ago were not fathered by him.

Chacon said if the "presumed" father obtains paternity tests that say he isn't the genetic father, often the desire is to "disestablish" paternity to avoid being on the collection end of child support.

Her office, backed by the state Attorney General's Office, has resisted doing that, instead leaving the decision in the hands of judges, who she said are ruling very differently across the state.

"We have had judges say that after 15 years, 'You're not Dad,' " while others say the opposite, she said.

On the flip side, family law lawyer Paige Bigelow said, "fathers" slapped suddenly with the same confession are being told by their former wives they have no right to remain a part of that child's life, even though they have been the "social father" for years.