Your Fault - Season 7 of Modern Family.
They stayed there for the better part of 10 years as Alex worked her way through first college and then law school, mostly supported by Haley who worked a series of low-paying jobs to keep them afloat, although their family was always there for them when they neede them.
For those years they lived quite comfortably, and were quite sad to leave once Alex started being successful, although Haley was grateful that she finally got to give up working and become her sister's housewife like she'd always wanted.
Just before they moved out of their first apartment Alex proposed and they quickly hopped on a plane as soon as Haley changed her second name as by that point getting married was way overdue as far as they were concerned. Just one year later Haley was pregnant with their first child.
The pregnancy and the first few years with Haley's little girl was a nightmare, especially with Alex working so much, but they were determined to have three children and they were so glad they did because their adopted son was good as gold, and while Alex's pregnancy hadn't been a walk in the park she loved the baby girl she got from it.
As convincing their families to pretend like Alex and Haley were a real couple for the sake of the children was the hardest part of her plan Alex was worried it wouldn't work.
However Haley was a masterful liar, and with over 10 years to practice Haley put on the performance of a lifetime, convincing everyone in the family, including Manny, who was arguably the second smartest after Alex of course, that their plan was what's best for the children.
After that they still got some funny looks from various family members, especially as they ended up with two girls and a boy just like their own family unit growing up, but most of the time they just shrugged off as the alternative was that the two sisters really were together, which most of the family still thought was ridiculous.
Life wasn't exactly perfect. They inevitably fought more and had sex less, mostly because of Alex's hectic work schedule and having children, but they made sure to find time for each other and never to go to bed angry.
And they got to grow old together, so there was that. Most of all they never stop being in love. If anything they fell even deeper for each other when they truly got a chance to be alone, regardless of how wrong some people might see the true nature of their relationship as.
Although they could never decide who was responsible for them ending up in this very twisted modern family, often teasing each other that it was 'your fault'.