So, I (32M) own a modest three-bedroom house that I’ve been paying off for the last ten years. It’s nothing fancy, but it’s mine, and I’m proud of it. My sister (29F) and her husband (31M) are the typical free-spirited types. They’ve always talked about quitting the rat race, living life to the fullest, all that. Well, a few months ago, they finally did it—they sold their house during a booming market, thinking the profit would fund a year-long break to travel.

They believed they could stretch the money by traveling cheaply, staying in hostels or Airbnbs, and getting by with occasional odd jobs. At first, they stayed in nicer places and ate out a lot, thinking they had plenty of cushion, but within two months, they were out of money. They underestimated how quickly expenses would pile up, especially with two young kids (7F and 5M) to feed and care for.

Now that their funds are drained, they’ve decided to stop full-time travel but don’t want to settle down yet. Instead, they asked to live with me, rent-free, for the next 10 months while they “figure things out.” They say they’ll still try to take some occasional trips if they find super cheap deals, but for the most part, they want to stay at my house.

I told them no. My house isn’t big enough, I don’t want the disruption, and I certainly don’t think it’s fair for them to live off me because their plan failed. I offered to help them find an affordable rental or even cover part of their expenses for a couple of months so they could get back on their feet, but that wasn’t enough. My sister blew up at me, calling me selfish and accusing me of being jealous of their “adventurous lifestyle.”

To make it worse, my parents are siding with her, saying that family should help family and that I’m being too rigid. The thing is, my parents live in a small apartment and can’t take in my sister’s family, which is probably why they’re pushing it on me. They say I don’t understand the “value of experiences” and that I should be more supportive. Some of our mutual friends are also saying I should be more understanding, but I think it’s completely unreasonable to expect me to house their whole family for nearly a year just because they didn’t plan properly.

AITAH?

She left the house at 5pm saying she was going to her brother's house for the night. Brother lives over 100 miles away, I happened to check the odometer (in MY car) because I knew the oil was due soon, and if it was too close I would have asked her to take HER car. When she gets back the next day, I see she drove less than 100 miles total.

When I first confront her, she says she doesnt know why the odometer says that, so I ask to see receipts for the gas she bought. She refuses, trying to make me feel bad for not trusting her. I start getting really upset and eventually she leaves, telling me she's done.

Finally that night she admits on the phone that she lied, and was drinking downtown and slept in the car. I don't believe her so I hang up the phone.

She has no reason to lie about this. She literally was drinking downtown with her friends a couple weeks ago and I was fine with it. She can do whatever she wants, I'm not controlling or jealous.

A few days later I ask her to explain what happened. She says she already did, I say "you were gone for 16 hours, I need more details".

Doesn't remember if she went alone or with friends.

Doesnt remember if she bought drinks, how much she drank, or what she drank.

Literally cant explain any details at all other than "I was downtown". Is getting upset at me again for even asking, saying she doesn't want to talk about it.

So cheating is the only explanation right? Lies about something for no reason, gaslights me when caught, refuses to elaborate on her backup story. I mean how much more obvious does it get?

Edit: To be clear, I had been checking the odometer every day, because the oil was due very soon. I have had car after car break down on me, I cannot afford another one. If it was too close, I would have told her to take her car, because she has one. Sorry if that wasn't clear, SHE TOOK MY CAR to do whatever she did. I didn't check the odometer in her car to try to catch her in something, I had no suspicion whatsoever