My SIL is 8 years older than my husband, though to know both of them you'd never know it. I sometimes feel certain the is adopted, they are so different. She is a habitual "bad decision maker", doesn't accept responsibilities, and is a compulsive liar. My inlaws have "helped" (enabled) her her entire life. She got married both times because she "Had to" (in my inlaws eyes anyway) and neither marriage lasted more than a year. She signed over custody of her 1st born to her (soon after ex) inlaws. My inlaws insist she was "tricked into it", but then she left her infant son 3 years later for them to raise. She just didn't want the responsibility of raising kids. Yet they never took custody because they felt sorry for her. They have spent no telling how much on her over the years, paying to help buy and furnish houses, help pay bills, not to mention pay all expenses for her son for his 21 years of life (and he's in college and still living with them and they still pay). We hardly get anything from them (nor does our son) and when she took the other two (college and HS at the time) grandkids back to school shopping (at Hollister, American Eagle, etc) and didn't offer to take ours and then gave him $20 to "buy some jeans" when he called her out on it, she said "well, I know you guys have the means to take care of his expenses". Yeah, but he's still your grandchild. We are always overlooked because "we have the means" to take care of ourselves. SIL works, sold her house years ago, lives with her long term boyfriend who lives in a paid for house that he inherited, and they have 5 vehicles and a Harley motorcycle between them. The only difference is DH has a college degree and is an engineer, where she never went to college and has always worked blue collar jobs. So that is how we "have the means" and she doesn't. She also goes to their house for supper every night and takes home a plate of food for boyfriend as well. It's ridiculous, but it's the way I've known it to be the whole 18 years DH and I have been together.
DH and I are the ones who purposely go over there after we have already eaten supper as we don't want MIL to feel like she has to feed us. DH is the one volunteering to help FIL with things around their house, he helps MIL understand her IRA and other accounts, and when MIL has had dr. appts/procedures/treatments (cancer patient) I am the one making sure I am over there cooking supper for them (and SIL lol) when she gets home so she doesn't feel obligated to cook for SIL and over exert herself. Not to mention we moved nephew in with us when MIL was hospitalized for 2 months when my son was less than a year old.