I had one of these, it wasn’t just the age difference, or the lying about it, it was the other lies he’d told as well (to maintain the age lie) that changed who he was.
Because of the “lost” 5 years, it looked like he’d accomplished loads over a relatively short period of time. For example, he told me he’d got a specific qualification whilst working simultaneously. But actually he’d had some midlife crisis, quit his job and let his wife hold down the bills and house and kids while he fannied about trying to “find himself” and then decided to do the qualification to try and get back into the workforce.
We “bonded” over how hard it was to work, plus train in a new profession, plus be a hands on parent (something I’d done) and I thought he was ambitious and hard working.
Once I knew his real age, the lies started to show and it demonstrated he was actually lazy and looking for his next meal ticket. He wasn’t a hands on father whose only reason for missing so much of his kids’ childhood was down to his job and trying to secure a brighter future for them, he was a hands-off father who had spent years unemployed (through choice) and STILL hadn’t done the school run or packed lunch boxes, despite his wife being the breadwinner.
Liars lie. You know he lied about his age, you don’t yet know what else he’s lied about.