Cease And Desist Letter From Father, But We Have Done Nothing And Don’t Know What He Is Referring To.

So I signed for a certified letter today that ended up being a cease and desists letter from my FIL. We worked for the family construction business (owned by my FIL and a business partner)up until April of this year. At that point my FIL fired me and my husband bc we were 8 months pregnant. My husband found a job with another construction company in July. Since then he and I have moved on. My husband works with 2 of the same subs from The family business (FB) but one we went to high school with and hang out with and the other has never asked any questions as to why my husband and I left the FB. The FB did not have the best reputation in my city. They were notorious for being slow to pay or not paying subs. having lawsuits filed against them(4 lawsuits in the past 2 years). And just general mismanagement. Well My husband saw a painter that he used to work with at FB at the hardware store 2 weeks ago and the guy thought my husband still worked with the FB and was asking what was the hold up with his money he is owed. My husband told him I don’t work there you would have to ask FB. My husband told him we were fired, did not say why we were fired. Then the painter asked if my husband thinks he will ever get his money and my husband said he didn’t know. He came home that evening and told me of the interaction. Then a week ago my husband gets a no postage no return address envelope left on the doorstep of his current employer. It’s a letter from his dad saying he knows my husband is making disparaging remarks about FB. Then yesterday we get an email from an attorney and today a certified cease and desist letter. Saying we have both been making disparaging and defamatory remarks about the FB and the owners.

Are we in trouble? We never signed an NDA. do we owe them any response? We don’t have money(especially this time of year) to hire an attorney. I’m included in the letter but I’ve been home with my newborn baby. It says we have to respond within 10 days otherwise they can take legal action. I just want them to go away. They have money and they will sue us if they can bc they are those types. How do I get them to leave us alone? Please help