DEAR ABBY: My husband’s best friend died when we were in our early 30s. His son, “Marty,” recently moved back to the area with his wife and three boys. We think of them as family.  My husband often needs help with heavy handyman jobs. (I was diagnosed with cancer and am unable to help him.) He frequently recruits Marty for this kind of help, and Marty always brings along his wife and kids. They don’t watch or discipline the kids, and I’m exhausted. Is it really up to me to parent their kids while they are here giving us a…