Their goal is to educate the public and lawmakers on what paternity fraud is and it's devastating effects.
"A lot of times guys have no idea, they assume they can get a DNA test and everything will go away and this won't be my child. But that's actually not true. They have to contest the paternity and they only have a small window of opportunity to do that."
That window is only two years from a child's birth. She says her group also serves as a voice for children who may also be victims.
"Medical history, inheritance rights, also to know who your family is and your biological father is," said Thompson.
According to the American Association of Blood Banks, 28-30% of fathers tested for paternity are not the real father.
Thompson said paternity fraud happens when there's uncertainty.
She said there are a few ways it can happen including being named as a father when a mother is applying for child support or welfare, when a man signs papers at the hospital claiming he is the father at the time of the child's birth and presumption of paternity - when a married woman has an affair - and the husband is presumed to be the father.
"It doesn't state that they have to give a truthful disclosure and therefore, that's when often time, paternity fraud will occur. Is when there isn't a DNA test done and they don't know who the true father is," she said.
Thompson said dealing with paternity fraud is a difficult process, but her organization is there to help.
"They often think they're alone, they think they're the only ones that this has happened to. And we connect them with resources," she said.
Thompson said her organization is currently working on a paternity fraud reform bill for next year in California.