DEAR ABBY: I have just learned that my sister’s husband of 35 years (I’ll call him George) hasn’t filed their personal income taxes going back a number of years. This has caused a lot of stress and anxiety for my sister, who recently underwent breast cancer treatment. Apparently, he hasn’t filed because of his inability to organize. (His family has denial issues.)

Their professional tax preparer has met with both of them and tried to work out a step-by-step program, but George consistently fails to meet the deadlines. I love my sister and want to be as supportive as possible, but I’m unsure what I can do. I have advised her to seek therapy. She has copies of business-related documents relating to the unfiled tax periods, but not enough information to file on her own.

On top of everything else, she has several relationship issues with her children that are causing her grief. What else can I do? — HELPLESS BIG BROTHER

DEAR BROTHER: Failure to file one’s taxes is a federal crime that could land your brother-in-law and sister in the slammer. That’s why you should urge your sister to do something she should have done years ago — take over the family finances.

She and her husband may need more help than their CPA has been able to give them. A group that I have mentioned in my column before is the National Association of Enrolled Agents (NAEA). These are tax specialists — some of whom are attorneys and CPAs — who are SPECIFICALLY licensed by the Department of the Treasury. Tell your sister to contact an enrolled agent by visiting www.naea.org. TODAY.

DEAR ABBY: I recently moved in with my boyfriend, “Teddy.” We are both in our 20s. Five years ago, he married his high school sweetheart. Two years later, she cheated on him and left. Teddy and I have talked about the situation countless times. I know he doesn’t love her anymore and cares for me a lot.

Abby, I lose sleep over their relationship. I can’t stop thinking about how she left him — not the other way around — and if he hadn’t caught her cheating they would still be together. I Google her to see if I can find out anything about them. I check her social media sites multiple times a day. I know I’m being ridiculous, but I’m obsessed with her!

Teddy is such a caring man, he tells me everything I want to know, but my obsession with her and their relationship is starting to get to him. I don’t want to lose him, but at the same time I wonder if I will have to leave because I can’t get over their marriage. What should I do? — OBSESSED IN OHIO

DEAR OBSESSED: There’s an old saying that applies to your situation: One man’s trash is another man’s treasure. Your boyfriend’s ex didn’t recognize what a prize she had, fouled the nest and threw him away. How lucky for you that she did.

I can understand your being curious about her; what I can’t understand is your compulsion to stalk her online. What she’s doing these days has no effect on you or your relationship with Teddy. If you keep this up, you will drive him away. If you can’t stop, find a licensed mental health professional who can give you the tools to overcome your insecurity. It will be money well spent.

Dear Abby is written by Abigail Van Buren, also known as Jeanne Phillips, and was founded by her mother, Pauline Phillips. Contact Dear Abby at www.DearAbby.com or P.O. Box 69440, Los Angeles, CA 90069.